This is my idea:i am going to give a different opinion. I know i am not nearly as knowledgeable as guys like SL, but please tell me if this makes sense.
When you do a conventional bench press, you're activating more muscles. You are going out of your way to arch your back, and pushing through your knees, which will activate your back a lot more.
However, when you put your feet on the bench and you don't arch your back as much, you don't get the same amount of force you get when you push through your heels, which would transfer the load more to your chest. Yes, you wouldn't be able to use as much weight as you would with a conventional bench press, but you would stimulate your chest more.
Again, please tell me if this is an inaccurate analysis of putting your feet up during bench. When i thought about this the other day it kind of made sense to me.
Lets say with no leg drive and no arched back you can bench say 200 pounds for 5 reps. Then you learn the technique used by powerlifters and arch your back, put your feet back and focus on recruiting the lats as a springboard, and from doing this your bench jumps up to 225 for 5 reps.
Now you see this thread and think hey why not try military benches, I bet you cant do 200 pounds for 5 reps, maybe you manage 185 for 5 reps purely because stabilisation and balance becomes an issue with feet in the air. But both ways - with feet on the floor but using no leg drive and with feet in the air with no leg drive didnt recruit the lats or use hip drive or use an arch to shorten the ROM. So if with feet on the floor you could bench 25 pounds more purely because you could balance better than why would you want to restrict your poundage and be wobbly on the bench, just because your using less poundage doesnt mean your chest will be doing more work.
It would be like squatting on a BOSU ball - yuor poundage would decrease cause balance would be an issue but that doesnt mean it would work your quads any harder...