Manufacturing most Toy Haulers is about building them cheap, er I mean low cost.
I'd say quality varies by year. Right now from what I've seen the Grand Design seems to be top notch, I'd also put the Desert Fox line up there too. But a couple years ago that may have been the Cyclone, before that it was another brand. Quality comes down to what you want and are willing to pay for. The more popular a brand becomes the more they produce the more they seem to start suffering from quality control.
I'd say the most common size for a garage is the 12' having things like a generator help in resale.