Hrmm.. ~525 rounds 22lr for <$20 vs. 100 rounds 9mm for ~$23 at walmart.
I can spend all day at Laguna Seca on the steel course and even play with the 300yd gong if I want. Or I can spend all day on the tin can range at Los Altos rapid firing.
Can't rapid fire the 9mm at any ranges nearby, and I'd be spending 5x as much on ammo.
Also, my wife likes 22's, so we go out together, and that's a huge plus for me. Even my mother said that our 22's were cute and she'd be willing to go sometime. So they seem fairly female-friendly which could be a good thing if you're trying to introduce a girlfriend to your hobbies.