I would recommend casting as wide a net as possible, there are a lot of manufacturers out there and it seems every year or two there is another one. However the 'big guys' tend to turn up far more on forums, on the road, more local dealers, more exposure, higher up in search results because they are more popular.
Going to an RV show will allow you to look at the brands represented there, sometimes just what the local dealers carry. Maybe some really big ones do literally have *all* of the brands, but I wouldn't bet on it.
As an example Northwoods (Nash, Arctic Fox, Snow River). There is one dealer in my area that carries these.. however they rarely ever have any in stock and at least in the last 4 years they have never taken any the local RV shows. RV show is a good start and a good place to get a broad look, just may not be the place to see everything.
