RE: Pulse XT vs Avistar
We can only make assumptions on your actual skill level. Asking what the differences between a high-wing and a low-wing suggest to me that you should park the Pulse XT until you can answer yourself.
Having more than one airplane is never a waste. After 20 years of flying, I still bring my trainer to the field every weekend. I just may meet someone who's ready to step up to a nitro rc plane.