Remember: Largest doesn't always mean they will have the manufacturer's you want to see or even the model or floorplan that you are interested in. But it's a start.
I always look for upcoming RV Shows in the area we're in from various RV sites that list nationwide shows. Then do a search online for the RV Show website. They usually give you dealers who are attending. Then I can find out if that dealer carries the RV's we're interested in. Plus if website provides a map it helps me to plan out the booths we want to see. Makes it a fun day trip instead of a long weekend & a confusing jumble of floorplans & decor.
I like to go to RV Shows that have Factory Reps. Information is usually slanted towards their product line, but you can usually find out some good information that a salesman from the dealer wouldn't know.
We've been going to shows in multiple states over for the years. We even made it to the Big Hershey in Sept of 07. They didn't have any Elite's, only Mobile & Selects. They had a good supply of 5er's from midlevel models to higher end Teton, Heartland, Excel & even a New Horizon.
We had our first look at a Tiffen MH. While we didn't talk to Bob Tiffen, the owner, the neighbors we had in the RVP did & they traded their Montana in for one....
http://rvtravel.com/05rvshowsched.shtml