Depends, man.
Point Man (SMGs) is good with the Silence function but bad with damage.
Riffle Man (AR) is good at doing damage and for rushing.
Sniper (SR) is good at doing damage, good for camping and good with very-long ranged combats.
I usually use Riffle Man. (I used to play with the M4 but then I changed to AK.)
And I also use Sniper. (Very good in Annihilation and Demolition.)
I like all of them but the i like the most sniper and pointman
the weapon class i prefer r different depending on the game. If its annihilation i use rifle man (AK 47) but if im playing demolition i use points man (uzi) and for escort i use sniper (sv-98)
Oh, and SR is also good at Escortion. XD
I prefer Assault cuz i pwn at M4A1 xD