If energy was pertinent to terminal performance in handguns, you'd be correct.
Actually I do think energy pertinent to terminal performance. It takes energy to alter matter. Each tissue bond that is broken takes its toll. The more energy available, the more bonds that can be broken. The more bonds that are broken, the more damage that is done. It really does not seem a whole lot different than automobile accidents. A bigger, heavier car going faster is going to do a lot more damage when it hits something. A .38 Spl when compared to a .22 mag is bigger, heavier and faster.
I also think momentum is pertinent to terminal performance and it mass times velocity. I think the heavier faster projectile will have better terminal results.