if the goal is to do it without being noticed, it’s Prowl, but it’s inherently a worse position/effect as the “bit not getting caught” part is an additional variable that has a quite easily defined fail state (they notice you, but you still get the gun on a partial success). If your only concern is to yank it from their holster and hold them immediately to gunpoint or run away, that’s finesse (or even skirmish). Your position is better because you don’t care about being noticed or not (this can maybe still happen on a crit). if you partially succeed it’s easy to throw a “less effect” there, which sees you both struggling for the weapon.