.32 - it's designed to function from a short pistol barrel. .22 Mag is really a rifle round and doesn't get up much steam in a few inches. I read a pretty good ballistic comparison a couple years ago, and .22 Mag was not shown to be much different from .22LR. Plus, it is not as reliable in an auto.
But if we're talking tiny revolver, .32 mag would be better than either.