There is no real answer to this but if made to chose i would go 9mm for self defense, and 357 if i am out in the woods worried about 4 legged creatures.
I have 5 guns that shoot 9mm, but can't say its my fave. My 38 Super can be loaded real close to 357 mag velocity and I can carry 17 rounds in an easy shootin' 1911. Yeah. 38 Super gets my vote.
9mm. Cheap to shoot for paper. Defensive rounds that are available will get the job done. Easy to control. Every hand gun I have is a 9. Plus a couple of .22's.
My favorite cartridge has a lot to do with the platform that launches it.
.45 ACP out of a full size 1911 Government.
So satisfying to shoot and it doesn't beat you up.
Next would be the ubiquitous .22 long rifle 'cause cheap plinkin' is good clean fun.
My oldest daughter used to like .44 Mag best but she has fallen in love with my Springfield Armory TRP 1911.
This summer I'll let her shoot them side by side and see what the verdict is.