For 100 bucks, versus 125 for a Big Stik, I definitely cannot recommend against the Avistar. Lots of people use it as their primary trainer and some use it as a second plane. The Big Stik is a high wing model, with tricycle landing gear, so there are some things about it that are similar to the trainers. The Big Stik wing has little dihedral compared to the trainers.

I guess the main difference I see between trainers and most 'second planes' is the fact that you always have to tell the more advanced plane what to do. That doesn't mean you're always having to wiggle the sticks though. The plane will fly straight and level, or in whatever attitude you put it, until you tell it to do something different.

When you fly your trainer: When you bank it with aileron, then let the stick go back to neutral, the plane eventually will tend to level the wings. A high wing plane with little or no dihedral (like a Big Stik), and most low wing planes, will tend to stay banked until you give opposite aileron to level the wings. My instructor taught me to do that with my trainer. He said, even though the trainer will try to level the wings on its own, it is better to learn to do it from the start.

I have only flown one low wing plane, a Sig Astro Hog (in my picture), and I did not think it was any different than flying a high wing plane. It does require me to level the wings after a turn (and point it where I want it to go) but it is very stable and easy to control.