Personally, I use my 3/8's impact gun more then anything. Mix it with some impact swivel sockets, and you have a tool you use for close to everything. I tell people all the time to get one, and no one listens to me (not on here), then they see me work with one, and they are like "No ****, I didn't know you could use it that much." Part of the problem is people are scared of it because the first time they use it with a swivel socket a nut or bolt goes flying about 20 feet, and the socket comes off if it's on an extension. But, you learn to be able to control it real good. Also, you do NOT need impact sockets or extensions with the 3/8's gun. BUT, I do run cheap Companion line extentions, which I have yet to break, and are available at Sears. They have the wobble head too with works pretty well. Yes, I have broken Snap-on and Mac sockets with the gun, they do eventually give up. No big deal, you just warranty them. Craftsman sockets are even better because all you have to do is run to the mall. And I would recommend 6 point sockets only with the gun. Unless, of course, you have a 12 point bolt.
I have never used a butterfly style gun before, I don't see the point

, but that means I am acting just like the people I tell about a normal 3/8's gun that don't understand, so maybe I'll pick one up.