Well, I like almost all (primary) weapons in Sierra 7.Only thing what I dont like that m60 machine gun which you get if you beat game on veteran/elite difficulty has unlimited ammo, its prettu unrealistic and make that weapon overpowered.But you get it when you have win game, so it isnt that kind of "roblem".
For me any weapon is great so it doesn't really matter which one I use. All the levels in any difficulty are really easy. I usually use the Colt M4A1, the HK G36C or the Benelli. On the other hand, I only use one weapon for handguns, the one with the silencer. I don't like the M60 though.