5x5 -split or full body?

One comment on the flyes with dbs- you don't want to do these heavy anyway, so the rep range you have now is fine. They put your body in a position where there is no bone supporting the weight. Personally I wouldn't do them at all because the potential for injury outweighs the slight benefit you'll get. There are better ways to target your pecs. Paused bench press where you pause the bar on your chest (don't give up tension, hold it there) for a 2 second count. DB bench with palms facing to get more ROM at the bottom of the lift. Cambered bar bench. etc etc.

Sorry I mis-understood your initial question.
If you want to do stronglifts 5x5 then it really doesn’t matter if you do full body or upper and lower split, as you have said you want to cut and maintain lbm, full body would usually be recommended but that is really personal choice. I have included some pro’s and con’s below to help you decide what is best for you

In general full body is better for beginners and those looking for an added ‘cardio’ effect when lifting

Full Body
Pros
You will be able to build a well balanced body by hitting all muscle groups in one workout
If you normally workout 3x per week and you happen to miss a workout, not a big deal as you have already worked all your muscle groups with just one workout.
You’ll maximize calorie burn and fat loss
Cons
It’s hard to hit a given muscle group very intensely, especially legs because the intensity can be too tough to handle along with the lengthy recovery time after a workout.
Can lead to overtraining
Intensity of full body workouts multiple times per week can be tough to sustain

Body Split
Pros
Superior for bodyshaping
Lifting weights should never be easy, but if you like lifting heavy, it’s more manageable if you are only focusing on 2-3 muscle groups at a time
Easy to switch up workouts
Cons
Less overall calorie burn
Muscle and strength imbalances, if your workout routine is not structured properly, it’s pretty easy to overdevelop certain muscle groups at the expense of others
Hard to miss / skip workouts

As a side note: You said you are eating at a deficit and you goal is to lose body fat while maintain lbm. While muscle size and strength would still be gained when doing 5x5, it is not the optimal routine when on a deficit because the low reps focus solely on strength, usually when looking for a more defined physique, it is achieved with moderate reps and weight and increased cardio. However if you have used this method during your bulk then you can cut using the same methodology as you did to build, with the same intensity and less volume, so maybe cut down to 3x5

Low rep ranges can still build/maintain muscle mass. I am a powerlifter who trains with low reps 75% of the time (1-3 reps per set) and my lean body mass is 250lbs+. The volume of training is what will determine how much muscle you build. Note prilepin's table. Say you do 3 sets of 8 reps of a given exercise, you would be limited to around 75% of your 1rm because of the higher reps so you would have completed a total of 24 reps at 75% of your 1rm. If you do 5x5 you should be able to work with around 80% of your 1rm, thus leaving you with 25 reps at 80% of your 1rm; assuming that your 1rm for a given lift is 150lbs that is 2,700lbs vs 3,000lbs. The moral of the story is 5x5 is great for developing strength as well as building muscle mass.

I switched to full body last year, and made far better gains than the previous year. (there were some other factors that helped this)

The main reason I think the full body workout 3X per week is superior is because in order to fit your workouts in you end up focusing on the lifts that really matter (squat, deadlift, bench, pullups) Doing more of these lifts more often has a much greater impact on your body than 50 minutes of arms and shoulders.

As you get more advanced it is difficult to make gains without really blasting a muscle group so you can no longer fit in a full body workout in a single session.

This is a good summary from Bodybuilding.com

Full Body Routines vs. Splits

The question often arises, especially from beginners, about what type of routine to use. Your buddy told you to use a full body routine, but the muscle mags suggest a 5-day "bodybuilder" split. You don't want to start off on the wrong foot, but there is so much information out there that sorting through what to do can be difficult.

This is some of my opinion on the subject, and maybe it'll help a few people out.


Full Body Routines:

In my opinion, this is the place for a beginner to start. I have many years of lifting experience, and have pretty much always used some form of bodybuilding split routine. However, if I had it to do over again, I would have begun with a good full-body routine, built around the compound lifts, done 3 times per week. When you are a beginner you don't generally have the muscular strength to work intensely enough, or with enough volume, to require as much recovery time as someone who is stronger or more experienced. If you are a young beginner, on top of that, you have very good recovery abilities due to high hormone levels. So, because you are recovered relatively quickly after each workout, you want to stimulate each muscle group more often to induce strength and growth.

Another reason to start with a full body program is that this gives you the opportunity to learn and practice the basic lifts: squats, deadlifts, bench press, overhead press, barbell rows, etc. Whether your goal is bodybuilding, strength athlete, sports, or just remaining fit, these really ought to form the basis of any routine. No matter what path you choose to "branch out" on later, these core lifts will serve you well.


2-Day Split Routines:

So the next question becomes: when should I think about split routines? In very simple terms, the answer is: when full body routines become too much. Usually, as you get stronger, it becomes very difficult to maintain enough energy to do squats, deadlifts, bench press, etc. all on the same day. You may also find that you want to add in a few isolation exercises to bring up your weak areas, or you may want to begin focusing more on each core lift. Another issue is recovery; as you get stronger, you are able to work out more intensely, and that means longer recovery times. So at that point, it makes sense to "split" things up by only doing a part of your previous full routine on any given day.

A logical place to make your first split is into an Upper / Lower type routine. This will have you doing your upper body work like bench press, rows, overhead pressing on 1 day, and your lower body work like squats on another day. Another way to go would be a "push/pull" type split where you do all your pulling exercises (rows, deads) on one day and your pushing exercises (squats, overhead press, bench) on another day. Exactly how you do it is up to you, but the point is to divide the workload per session. This will give you more time (and volume) per body part, and also give you a bit more recovery before you work that muscle again. Most people will typically cycle through a 2-day split like these twice per week. So instead of every muscle being stimulated 3 times per week with the full body, now it's twice per week with the 2-day split.


3+ Day Splits:

3, 4, 5 (or more!) day splits come in when you again feel the need to divide your workload to match your recovery abilities, or increase the amount of work you want to do on specific muscles or lifts. Generally, these type of splits are mostly bodybuilding related, but even strength athletes may chose to split so they can work on speed lifts one day, strength work another, etc.

At this point (speaking to bodybuilding) many lifters will only hit each muscle group once per week. This has the advantage of letting you really hammer a muscle group with a lot of weight and volume, and then give it plenty of time to recover while you're bringing the pain to the next group. Your full body effort is broken down into segments that are manageable from a workload, energy, and recovery standpoint.

If you are an "experienced" (older) lifter with decreased recovery abilities (we all ain't as young as we used to be), this type of split often is useful for staying healthy due to the increased recovery time per body part. The kids might not think it's important, but your tendons might.

There are so many variations of splits that I won't even attempt to detail all the possibilities. If you follow the advice in this post, by the time you need a multiple day split, you'll know your body, your goals, and have a pretty good idea of what you want to do.


Final Thoughts:

I believe it's a logical notion to start with a full body routine, and begin splitting only when you feel the need to increase your recovery or increase your volume. If you stick with the concept that you're trying to hit a muscle as often as you are able while still recovering adequately, and let that be your guide, you'll do okay.

Hopefully, this gives some food for thought to help you decide what type of routine you should use. Ultimately, however, it's worth saying that you can do fine with any well-designed program even if you begin with a split routine right from the beginning.

Low rep ranges can still build/maintain muscle mass. I am a powerlifter who trains with low reps 75% of the time (1-3 reps per set) and my lean body mass is 250lbs+. The volume of training is what will determine how much muscle you build. Note prilepin's table. Say you do 3 sets of 8 reps of a given exercise, you would be limited to around 75% of your 1rm because of the higher reps so you would have completed a total of 24 reps at 75% of your 1rm. If you do 5x5 you should be able to work with around 80% of your 1rm, thus leaving you with 25 reps at 80% of your 1rm; assuming that your 1rm for a given lift is 150lbs that is 2,700lbs vs 3,000lbs. The moral of the story is 5x5 is great for developing strength as well as building muscle mass.

As a powerlifter I'm guessing your goal wasn't to cut body fat% and that you weren't on a deficit either, which is what the OP is trying to do. Lower volume training is perfectly adequte during this period. Muscle mass cannot be gained and strengths gains are minimal while eating at a deficit and there is no way anyone should be trying to lifting 80% of their 1rpm during a cut IMHO.

Notice on my post where it says lost 33lbs? I'm obviously on a cut and it is important to lift above 80% 1rm while on a cut to maintain strength levels. The only way to increase strength on a cut is to increase neurological efficiency which is done my training with dynamic effort or by lifting above 90% 1rm.

The moral of the story is 5x5 is great for developing strength as well as building muscle mass.

As a powerlifter I'm guessing your goal wasn't to cut body fat%....which is what the OP is trying to do.
Muscle mass cannot be gained and strengths gains are minimal while eating at a deficit....

Notice on my post where it says lost 33lbs? I'm obviously on a cut and it is important to lift above 80% 1rm while on a cut to maintain strength levels. The only way to increase strength on a cut is to increase neurological efficiency which is done my training with dynamic effort or by lifting above 90% 1rm.

5x5 is great for developing strength and you may see minimal size gains too, agreed, but muscle mass gains will not be seen whilst eating at a deficit.

Your post does not state you lost 33lbs, your ticker does which is not an indication of what you are currently eating so sorry it was not obvious you were on a cut...mine shows I've lost 19Kgs but I'm currently on a bulk.

The OP is not trying to increase size or strength but drop bodyfat% which in turn is not correlated to weight loss.

I'm very suprised you are powerlifting whilst on a deficit but each to their own and I'm glad you have been able to improve you strength whilst on a deficit but as you stated strength has a lot more to do with just muscle mass, it's also the CNS's ability to recruit motor units...But there is no way to get round the fact that building muscle is an anabolic process i.e. building more complex structures from simpler ones. Your body will always try and maintain homeostasis so at any given point, your body will be in either of two states: an anabolic state or a catabolic state. So trying to build muscle whilst on a caloric deficit is at best a totally inefficient process. When on a deficit and you lose weight, you will lose muscle and fat through catabolic pathways i.e. breaking down complex structures into simpler ones, the goal is to minimise the muscle lost and therefore the best way to maintain muscle mass is to use ANY lifting programme in which you have seen good gains but at a reduced volume to prevent burn out.