There is no loser -- either one works very well.

The Superstar is somewhat better as a primary trainer, somewhat tougher, and also larger (easier to see in the sky).

The Avistar is acceptably capable as a primary trainer, lighter (works better with a low powered engine) & noticeably more agile.

While the Avistar is fully aerobatic to begin with, the Superstar is reasonably easily modified into a highly capable hot-rod.

Make your choice -- they are both good.