It really depends on what you mean by 'plink'.
If you just punch holes in paper, by all means get a 9mm. At $12/box it's the best deal running on centerfire ammo. Controllable recoil and accurate.
Now if you actually shoot interesting stuff like pins, TV sets, steel cans, empty propane tanks etc the .45 makes for a lot better time. For example, my 9mm FMJ will go right through most crap at the range, barely moving whatever it hits. Now the .45 on the other hand makes the sucker JUMP and DANCE...much more entertaining. It's one of those calibers that makes your buddy say, "Hey man, watch this!".
Skip a .40...too damn snappy. I don't like mine. It may get sold soon.
My favorite piece right now is the CZ 75BD 9mm with the extra Kadet .22 kit. Set up some cans, spinner targets and clays and you have HOURS of fun. Shot a whole 550 count box today and was disappointed I didn't have more.