Energy isn't the only response you can measure, penetration is another factor.
Guns don't kill people. Apes with guns kill people! - Robin Williams
9mm, 40, .45 JHPs are statistically a wash when it comes to real world effectiveness.
All handguns are underpowered and the stats show that well over 50% of people who are shot with handguns in civilian life survive and continue to live normal lives (typically criminal ones).
Shoot whatever floats your boat or buy a .500 S+W.