Depends...
If you wanted a real big screen, get a 30" ACD, though there would be more wires, and there would be no iSight or Mic built in...
If you just want a 24", with an iSight and Mic built in, plus less cords, get the 24" ACD. If I were you I'd get the 24" ACD.
And if you can't afford those two, you could get a Dell screen, 20", 24" or 30"...