Weight training with cardio

This is interesting. I'm in Week 6 here. Workout intensity is the same/working in high end of heart rate zone. Workouts have been 30DS & 30 mins walk/run intervals on treadmill or outside, increasing intensity as I gain stamina. I've had good losses up until this week and last, where I can't seem to budge. Seems too early for a plateau. Calorie deficit hasn't changed much. But what I have done different this week and last compared to the weeks I've been losing 2 and even 3 lbs is my 30DS & interval cardio was one workout, where the weeks I was losing good, I was separating them. Could this be why I'm seeing a difference in loss amts?

It would be irresponsible guesswork on my part if I said one way or the other what was causing your stall in relation to any weight loss goals. There are so many factors at play that it's hard to nail it down. We can go over a few of them though so you can be aware of them.

1) A good reason for the difference might be intensity level. Combining two exercise types together means the one you're doing second is probably suffering from a lower intensity even if you're pushing yourself. The overall calorie usage would then be lower.

2) Daily stress in life? Cortisol is your stress hormone which affects fat gain and weight loss in general. Any increased stress in your life will increase cortisol and that can delay weight loss.

3) Speaking of cortisol, eating too few calories for an extended period of time will also raise cortisol. It's the body's way of making sure you hold onto fat for times of starvation. If you've been on a constant diet for 6 weeks, that could definitely be a reason why. Maybe it's time to take 2 days and up your calorie intake by 500 or so to normalize your cortisol as well as your ghrelin and leptin levels.

4) Water weight. Change in weather, sodium intake, diuretics in the diet, and increased carbohydrate intake can make you hold water differently. If there are changes in any of those things, you might just be holding on to an extra pound or so of water.

Anyway, like I said, there are a lot of factors. If you don't have enough time to separate your workouts then keep doing what you're doing. If you can separate them then it's something you should look into for maximum benefit.

The original question was "what burns more fat?". Separate the two if your goals are specific to getting better cardiovascularly or trying for a max effort lift. If your main goal is simply maximal calories burned, then why the need to separate? You will still be efficiently burning maximal amount of calories in a shorter period of time, while still achieving strength gains (If done properly).

I currently do P90X, and my heart rate gets into the 150-160 range for 75 minutes during the strength training days. So I do burn quite a bit of calories that way, I sweat buckets too

When doing cardio, it is even more, my heart rate goes up to 175-180, and I burn more over a longer period. I still run for 60 minutes though.

I don't believe that 45 minutes is extreme and the body will stop burning fat etc. I don't care if you are a pro athlete or Joe Schmoe, workout for 60 minutes, you'll get 60 minute+ results, workout for 45minute, you'll get 45minute+ results...just listen to your body and don't over do it.

I sometimes Run for 45 minutes first before doing the 75 minutes strength workout.

Also, make sure you have some sort of recovery drink afterwards, it will help restore protein and heal your muscles, because you WILL burn some protein stores as well as fat with a crazy good workout. I use chocolate milk because it has a high carb/protein ratio