IMO buying an ARF is a good way to get into the air quickly and you can then decide if you want to build your second (or later) plane from a kit. I personally enjoy building but not all do or have the time. ARF quality is good these day especially in the trainers you have mentioned. I have instructed with both the Alpha and Arrow and have owned a kit built Eagle 2 and flown it (not instructed with it though). I see no reason why it would not be a good trainer though.
I realize I probably haven't helped you choose but I haven't discouraged you on any either I hope.

Do you still have radios and an engine? If not you may wish to consider an ARF although I would prefer to choose my own radio/engine setup if I were you.

I will add that the Arrow does seem to have a little more performance than the other 2 IMO with the same engine.