Superstar has a flat bottom wing for maximum lift and stability. Avistar has semi-symmetrical wing which is not totally flat on the bottom. Avistar has to fly and land slightly faster than Superstar because the wing produces slightly less lift. I have seen Avistar referred to as an 'advanced' trainer or even as a 'second plane.'

With an instructor you can learn on either plane. Just watching students who have come through our club (I am a 'lifetime' student), I think the guys who use a trainer with a flat bottom wing seem to learn faster than the ones who start with an 'advanced' trainer with semi-symmetrical wing. This is a subjective observation on my part since every student is different.