My rankings
for Power
They all shoot stick and shock the same.
As to what I think is the best, well, that's really up to what you're doing. Personally, I like a little something like this.
Qualities: Hawkeye + Ambidextrous
Guns: 2x Ceska Black Scorpion
Mods: 2x (Barrel Reduction, Chameleon Coating, Easy Breakdown, Extended Clip, Personalized grip)
Accessories: 2x Gas-Vent 3
Ammo: Combination of Stick-n-Shock and Tracer rounds.
The guns are -3 to spot when assembled and can be disassembled to get past security.
Can BF 2x per gun per pass without penalty, and can do that for 7 passes in a row without reloading.
Tracers provide no bonus within 4 meters, but provide +1 to each burst with each gun from 4-12 meters, and cancel out the -1 range penalty from 12-24 meters. (Most "sneak a gun" situations won't have engagement ranges beyond 20 meters anyway, unless you're in an airport or something.)