I think how big is big or how small is small is all relative to where you are. In my club, my 60 size airplanes are among the larger ones, there are a few larger ones in the 120 size but very few. To me, in my opinion, big is when I need to have high torque servos to control the surfaces. That just about puts it outside my price range, so I stay with average size (with respect to my area) 40 - 60 models. I love watching larger ones but it just isn't in the budget of most of the members of my club.
I think we need to introduce another category here, and have small, medium, large and 'giant'.