Only the 5.1 is an actual Hi-Capa, which is a sort of copy of the RS 2011, itself a 1911 style gun with a double stack (wider) magazine. So with the 5.1 you get a lot more gas capacity due to the bigger mag but the grip area of the frame is a lot fatter, vice versa for 1911 style guns, so pick your poison.
The Night Warrior is basically just a 1911, bit more modern styling. The Desert and Foliage Warriors are slightly shorter barrelled 1911s. Strike Warrior is smaller again. Basically all of them are the exact same gun to break it down to the very simplest raw terms. You lose a bit of muzzle velocity as the barrel gets shorter, that's about it. There is no 'best' of the lot and that term is far too broad and generalised.
Pick whichever one you like the look of. Or if you want more choice in holster options get the standard 1911A1 or MEU, not having the rail on there means they'll fit more holsters on the market (or unscrew the rail from the Night if you don't mind 2 small holes being left there).
