well
I just finished teaching a friend of mine and he has the Tower 60 trainer and OS-65LA... Runs flawlessly out of the box and has enough power to Hover the trainer, and it is not even broken in! (No, I am not kidding...)
I have the 61FX and it runs prefectly but the Tower-75 has quite a bit more power...
TT's are great motors also-
I would probably get theTT-61, Tower-75 or OS-61FX just because when you move up you will want that extra umphh.
Good luck!
james