well, maybe the way to look at this will be this way, since I've owned both, 9 mm -45, and they both worked just fine in both full auto versions and semi(pending mags mostly and ammo)
and since they mostly just spit ammo down range
if you wish to buy one, buy the 9, ammo will be cheaper for you to shoot it?
was at Cabela's yesterday and they had decent 9 mm on sale 10 bucks a box LOL


if you want one have at it, just don't think its a collectible like military gun, its just a gun, and with that, if you want one, get one, its your life, enjoy it how you like!