One spews its spent shells out onto the ground, the other keeps them in the cylinder until emptied and replaced.
In the revolver, you have a speed loader, that permits reload of the entire cylinder with one device, like the replacement of a magazine.
The gas operated weapon is faster, and I own both, but my preference is a S & W 357 Magnum, loaded with hollow points.
Any gun is better than a hammer, because even when out of ammo, use can use the gun as a hammer:)
I think there is a lot of truth in KYJim's Rules of Carry:
1. Any gun is better than no gun.
2. A gun that is reliable is better than a gun that is not.
3. A hole in the right place is better than a hole in the wrong place.
4. A bigger hole is a better hole.