The way skills handle it, being good with pistols or with SMGs has the same disparity of skill as being good with halberd or longsword or rapier+dagger. But there is a pit of experience between bladed (dagger) or bladed (2 handed sword), but there isn't really as much between two pistols that just require a general know-how of hand guns.The way I see it, being good with pistols and being good with SMGs are two different things.
At least make strong synergies, stronger than for weapons in AoD where system punished using more than 1 weapon.