Is a revolver stronger than a pistol?

It's the round which makes the difference, not the pistol. A .45 automatic pistol is going to be more powerful than a .38 revolver, for example. There are revolvers chambered in cartridges such as the .454 Casull and .500 S&W Magnum, which aren't available in any automatic pistols, but it's still ultimately the round which matters, and not whether it's an automatic or revolver.