RE: Tower Trainer vs Avistar
I was also stuck between the tower and the Avistar. I went with the Avistar as it had a semi symmetrical wing along with a bit less default dihedral. Which allows the plane to be a bit more aerobatic while still having all the characteristics of a trainer.
If you are on a tight budget, I'd go for the tower, it's still nice plane with MUCH better build instructions.
If you got the extra cash, you will not regret buying the Avistar. It's a very nice plane and built VERY well. The instructions are sub-par and not included so you have to get them from Hobbico's website. But I referenced the manual for the tower more (It's the same build directions wise).
So far it's been going great with the Avistar, got about 25 or so flights on it now.