Are Pistols more powerful or revolver?

It all depends on the length of the barrel, the caliber, and how much blackpowder you pour down the barrel.

A pistol, which is a single shot muzzleloading handgun was around .50 cal and loading 40 grains of blackpowder and a patched round ball shoots at around 750 fps. A revolver, such as the .44 cal Colts and the .44 cal 1858 Remingtons used during the Civil War loaded around 35 grains of blackpowder with a slightly oversized ball, around .451 or .454, can spit those balls at around 800+ fps. The 1847 Colt Walker was a .44 cal open top revolver, but on a much bigger frame. The gun loaded weighed a good five pounds, and it had a larger and long cylinder which held more powder, and could spit roundballs at over 1200 fps. The black powder Colt Walker is regarded as the most powerful commercially manufactured repeating handgun from 1847 until the introduction of the .357 Magnum in 1935, and has a muzzle energy nearly exactly the same as a 4-inch-barreled handgun firing a .357 Magnum.