Air nailers are faster but I've noticed that faster sometimes means sloppier. The professionals that redid the house didn't always notice when they just missed the stud (and hand nailing you WILL know if you just caught the edge and went out the side), sometimes the nails don't go all the way in so you have to whack them with a hammer anyway (or not notice and leave it to the homeowner).
I've often said I hit the nail on the head more often than a professional carpenter. Of course that is because *I* HAVE to hit EACH nail more often to drive it in. No "tap, BAM, BAM, BAM and done" with me doing the nailing. No, it is more "tap .. tap.. hit .. hit OK, probably in solidly enough to take my hand off and hit it hard. HIT HIT OOPs, caught the corner, bend it back straight, HIT HIT"