There's a reason carpenters use nail guns. Try it and you'll see!
All power tools have trade offs vs the manual alternates, often tipping towards their use, but not always.
I have had success on an occasion using a belt fed screw gun when fitting plaster boards, especially for ceiling boards.
However I don't do joinery often enough to justify the use of a nail gun.
Another thing - a hammer requires 3 hands: 1 for the hammer, one for the nail, one for holding the piece in position. A nail gun only requires 2 hands.