We full-timed for 8 years in a 33' 5th wheel and another 8 years in a 40' motorhome. We fit in exactly the same or same kinds of sites. Absolutely no problem. The reason we switched to a motorhome was that we got tired of driving the big truck around and Jeeping gave us much more enjoyment siteseeing in the boonies.
We prefer public parks vs. private RV parks. Our 40' fit in many national parks, state parks, national forests, COE, county and city parks. We boondocked on national forest lands and BLM lands and also fishing access spots in the West.
My suggestion is to find a good manufacturer, then select a floorplan from what they have to offer. It doesn't do any good to find a floorplan with a RV that is not reliable and cheaply made if you're going to full-time. You will be living and traveling 365 days a year for years.