I also got the Littmann Cardiology III. Not too expensive, sounds great (as far as I can tell).
The general consensus at my school seemed to be that unless you are really planning on going into cardiology, it doesn't matter which one you get.
The 27" tubing is definitely the way to go, because otherwise you are basically sitting in your patient's lap to listen to their heart/lungs.
I went with a color other than black, because everyone gets a black one, and they have a tendency to develop legs. Mine is navy, and I think I'm the only one with that color (or almost the only one).