Miscellaneous factors

The damage is identical, the penetration power is identical and the rate of fire is identical. The silencer and accuracy are the only two real factors that should affect your decision on a practical level. However on an unpractical level of decision making, the USP-S looks much sexier than the P2000, this isn't to say that the P2000 isn't a good gun, it just looks really ugly and a lot of the skins for the P2000 are relatively ugly too, whereas I find that the USP-S skins are amazing: