First of all, this is the handgun forum, not the "machine gun" forum.
Second, the 5.7 round was designed to shoot through body armor from a handgun. To my knowledge, no 9mm round does that from a handgun.
3rd, try shooting the so called 5.7 FMJ, non expanding, underloaded, practice round into a simple 2.5 gallon jug of water. Then try it with any 115-124 gr. FMJ 9mm round. The results aren't even remotely close. So believe whatever you want. E