The problem with worrying about numbers like Power is they aren't even close to judging a bullets performance on a live target .
Bullet design and construction play a huge part in the overall equation .
Say you want to hunt deer and I give you the choice of two guns a 30-30 and one of the hottest 22 centerfire magnums made .
You can probably find 22 center fires that when you look at only the raw power numbers will beat a 150 grain 30-30 bullet and think you've chosen the best of the two guns for the hunt .
Problem is when you shoot the deer in the shoulder your 22 traveling at over 3,000 fps is going to hit the bone and shatter into pieces and never reach a vital area where the 30-30 is going to break the bone and continue on into the lungs killing the deer .
The reason is most 22 centerfire bullets are designed for rapid expansion to kill varmints while the 30-30 is designed more stoutly to penetrate on deer sized game .
Then when you get into the subject of humans and self defense you get a whole new set of completely unknown variables , is he standing behind a car , a tree , a simple bush , what is he wearing ? Only a T-shirt or a shirt and denim jacket or perhaps a leather Bikers jacket ? What if he has a book in his pocket and you hit that ?
I hope you see why power alone really doesn't mean much .