That's like asking, "Which is better, a B-52 or a Piper Cub?"

What's "best" depends upon the task(s) you wish to perform and the conditions under which you wish to perform them.

For me, either a revolver or semi-auto are perfectly adequate and I carry both.

Working in a CPZ, I don't carry as much as I used to, but I mostly carry a Model 36 in a pocket holster because it's the smallest firearm in an effective self-defense caliber which I own. A small semi-auto like a sub-compact Glock in 9x19mm would work as well.