I have flown both (learned on a SuperStar ).

They are both excellent planes. The Avistar is going to land a little faster because of its semi-symetrical wing, on the other hand it is going to handle windy conditions a little better than the SuperStar because of better wind penetration, again due to its semi-symetrical wing.

The SuperStar is going to be a little more stable in the air since it has a bit more dihedrahl (the amount the wing tips are raised ) than the Avistar and the SuperStar is more of a "floater" than the Avistar.

Both planes will do a reasonable amount of aerobatics.

If you go with the SuperStar, set all your control surfaces to minimum. The suggested throws will make the plane very sensitive for many beginers. I don't know if the Avistar has the same sensitivity as the SuperStar.

I don't feel you will go wrong with either one.