Depends on the situation I guess. I have both maxed out and use Bladedancer mostly on patrols (low level enemies) and Gunslinger during strikes. And since I'm terrible in Crucible, Bladedancer helps me most of the times getting one or two kills more. Although I still get killed regurarly while bd is active so all the people complaining that it's op are full of bs. It actually takes some level of skill to get kills with it in pvp. (Which I'm sadly still lacking :-) ).

Neither. I usually just walk around fully super charged and never pop it because neither are good in pve. Damage is bad, range is bad, accuracy is bad. All around bad.