I like 9 because I get lots of hits with it.
Hits are important.
I like it because I don't... and because I have fifteen shots per mag, and can empty both mags into the target in tens of seconds, I can make up for it with volume of fire. :-)
Second shots are easier with the 9mm.
The second shot is the reason why law enforcement opted for the 40cal instead of 10mm when they realized they needed more power than the 9mm or 38special.
10mm is just too much recoil for a accurate second shot.