Auto-
Pros-rapid fire, some have hammerless designs, more magazine capacity.
Cons-Some say they are more succeptable to jamming, a little more complicated to shoot.

Revolvers-
Pros-point and shoot, easy to operate, come in stout loads like a .357 mag, rarely jam.
Cons-pack a few less bullets in the cylinder, some might say not as fast to shoot.

I choose to own both! There are all sorts of opinions, just go with what you can shoot well and what feels comfortable.