I agree with Hoss and Tim that bigger planes are easier to learn on, and also agree that smaller engines will allow things to happen a bit slower. I have a Tower Hobbies Trainer 40 with an OS Max .25 for power and it does just fine with the original wing and with a new 82 inch wing I built for it to get back into the hobby after a ten year break. Check out this YouTube video I've put on RC Universe before:

http://www.youtube.com/watch?v=4EkaU9emYWU

The big wing makes it a great trainer as students can see what the plane is doing so easily.