I've used 21 day fix as well. I've also done Les Mills Combat and Body Beast. All three programs are awesome. 21 day fix is a great program to start off with and learn how to eat right. Combat is a great program to shred your stomach muscles. I used 21 day fix meal plan with Combat as well. Body Beast is a weight lifting program and is great if you just want to tone or build muscles. All Beachbody programs are great, but right now I am just using myfitnesspal to keep track of what I am eating bc I have developed some type of nerve issue in my upper thigh. So until I get a proper diagnosis, I'm choosing to not workout. Maybe some upper body stuff, but i'm also having back pains so i'm trying to just watch what i'm eating at this point. Definitely add me. I would love more friends to motivate me and talk to when I can.

I like 21 Day Fix workouts a lot. I have never done the program as it's written, though. I use the weight workouts only and run on alternate days. I also have 21 DF Extreme, but I have only tried one of the workouts from that program. I think I'll like it, too, though! I also love Chalean Extreme. I have Piyo...meh...can't stick to it. I also liked Les Mills Pump, but I'm not sure they even sell that one anymore.

Ive done the Turbo Jam and Turbo Fire programs, Turbo Jam is great kickboxing beginner workout and Turbofire is higher level, both are superfun and easy to do in a small space (i.e. apartment) when can't make it to the gym. I love Chalene Johnson the instructor too she is motivating without being annoying!

I've done P90X3 and 21 Day Fix Extreme several times but not full rounds.
From just the results I got, 21DFX is good for a short-term, event-focused type of goal and helped me to keep my workout routine on track (say, pulling me back from a random, not-planned, purely cardio-focused weekly schedule). P90X3, on the other hand, is good for more advanced goals (I think). For me, it's not just for weight-loss purpose but also structured muscle strength improvement. IMO, it can't replaced other progressive weight-lifting beginner's programs, but I like the weight-training part in P90X3 for muscles I don't get trained much (I'm super weak in pull-ups)...
I didn't follow neither nutritional guidelines cuz I felt like it's for real beginners who just started learning the basics.
Unfortunately, I can't really stick to one program long without feeling boring quickly. That's why I always mix them up with programs from Les Mills (from Les Mills On Demand) and only plan to start another half-round (first two months of P90X3, to be precise) when I feel like I need another "reset" from a chaotic, non-planned schedule.