Fwiw, the Hobbistar 60 is a great flying plane, pretty much exactly like an Alpha 60, though the Alpha's 3-blade prop does allow the Alpha to slow down faster on final. The Nextstar really doesn't fly anything like a Hobbistar, the .40 size version of a Hobbistar is probably the SuperStar, which is also a nice flying trainer in the .40 size.

One of the best ways to get off of rough grass is to convert a trainer to a tail dragger and put on big wheels. I have an LT-40 set up that way, and it's a great short/rough field plane. And a little slipping on final will allow you to land it pretty much anywhere with practice. (the other day, we had a roughly 100x30 ft area marked out in the middle of the runway. The LT-40 with an Evolution .45 could take off and land entirely within the box, including roll-out).

Like other guys said here, the 60 size trainers do fly a little better and are easier to see, but there really isn't a huge difference between them and the .40 size ones.

A note on using the rudder, using the rudder when you exit the turn to cancel out adverse yaw will make it easier to exit the turn exactly on the heading you want. It also seems to reduce ballooning up. Most trainers will slip slightly through a turn if you don't enter with some rudder coordination. Then, when you start to roll out, the nose will slide sideways, going "downhill" and over-shooting center. The result is a slight dive and usually turning father than intended. Most guys learn to just exit the turn early to take this in to account, but you'll find that you can start and stop a turn faster and more accuratly if you use that rudder.