SMG's are more versatile in their range and do not suffer from the hit detection problems that shotties sometimes have on the server. Unfortunately, they take up a primary weapon slot instead of a pistol slot - so I use shotties a lot more, because then I can have 2 primaries (AR+LAW or SMG+Sniper Or MG). If SMG's used pistol slot (which is actually more justifiable than putting shotties there), then they'd be teh win.
EDIT: Just read that I should include what ones I've tried.
Shotties: I've used M590, the spazz, double barrel. Never tried the Supply Case versions. When they decide to register hits, both the shotties are nice... although the m590 can kill in one hit, if it does not then you can die before unleashing the second. The spazztastic on the otherhand will nearly always kill in 2h, and the second one comes pretty quick. Still like the m590 because I get better success from med range if I need it, but not sure if that's changed with the latest patch. The double-barrel doesn't impress me at all.
SMG's: Tried all of them except the K7 and K1A and the Rail MP5. Uzi is a nice cheap bullet hose, MAC-10 doesn't have much going for it except you can run at almost knife speed while still having an offense (good for CTF), P90 is a beast but runs out of ammo too fast and I don't like the accuracy at the point that you need to land the last 2 bullets. MP5 is a little too weak for my taste. UMP is The God Of Death.
