I almost always go small on the engine. And folks are always asking what I have on that bird. ( they perform well ) Going small has its advantages. For one thing, the taste of the airframe isn't overpowered by the characteristics of the engine. To me thats the big reason. But prop clearance, run time, wieght, less vibration, less reinforement because less vibration, and smoothness all resutlt from going small.
I ordered a CG Ultimate once, it was damaged in shipping. The company and I had it out. I didn't order a replacement after I shoved it down thier throat with the help of the good folks at Visa . However, at the time, I was in the same predicament. A 60 or a 90. After seeing the plane and handling it, but never actually flying one, I was leaning towards the 90. The 90 is the same size, and I believe it weighs slightly less. They do shake more. But the Ultimate is one of those birds that really shines with a big engine. I don't do 3D. But vertical is vertical. And an Ultimate can't have too much of that.
So, what am I saying ? You have zigged where others have zagged. Thats not a bad thing. You might fly your plane slightly differently than others might with a 90. An entirely new style of flying might be revealed to you that you might have otherwise not stumbled upon. Its Zen and the Art of Aircraft Maintanence. Live it your way and fly it your way.