Going used is always a good idea, especially due to the fact the value decreases quickly when purchasing new. I would suggest that while attending RV shows is always a good idea you might be better off visiting RV dealerships that have a good number of used units on their lots. You can go through those units to see how size, layout, and interior quality is for the various brands. You might even be able to rent a unit that you really like. Salespeople may be willing to let you rent especially if you are interested in purchasing.
After going through many different used units you will quickly be able to determine which ones you prefer.