My RV is 30 feet from tip-to-tip, and I have been in many campgrounds during my coast-to-coast trips.
Some sites were a breeze to pull into, and some were a (lets see, what's another word that starts with b ?).
A very few were impossible. Older campgrounds built for tenting, or pop-ups.
Most of the camp sites where I parked my 30 footer, I could just as easily have parked a 38 footer. But not all.
So if you are going to spend time in older campgrounds, or state/federal parks, you might want to stay small.
But if you camp in newer, resort type campgrounds, get the big one, assuming your truck can carry the weight.