First choose which caliber you want to shoot most, 9mm, 5.56mm, or 7.62mm NATO. If you don't want to invest in another caliber, then the POF5 is the way to go. Lots of after market parts and armorer support out there for the HK94 based platform. The POF5 with an arm brace is as close to a real MP-5 without having to get the ATF involved. I have rifles in all three calibers and prefer the 9mm platform for it's controllability, ease of assemble/disassembly, availability/cost of ammo, and lastly being able to shoot it in pistol ranges instead of rifle ranges. Once it a blue moon I will take it to the rifle range and shoot silhouette targets at 100 yards, yes 100 yards. Also I made 100 yard bowling pin shots with it. Granted the bowling pins just fall down like it was just tipped over and not jump in the air and tumble like the movies, but it is a makeable shot in the kneeling /prone position not all the time of course. Either way good luck in your decision.