Much harder to find campsites at state and federal campgrounds if you RV is longer than 28 feet. A slideout will make a big difference in living space and I would go with a shorter RV with at least one slideout.
I did a check awhile back of campgrounds outside of Yosemite. This is what I found in terms of size of RV and campgrounds with spaces large enough. It overstates the reality of the situation as a campground that has 10 sites large enough for a 35 ft. RV may have all of them taken when you arrive but have lots of spaces available for shorter RV's to use. Or you can elect to stay at private RV parks and pay up to 10x as much.
16' RV - 211 campgrounds 100% of RV campground
21' RV - 180 campgrounds 85%
25' RV - 150 campgrounds 71%
30' RV - 138 campgrounds 65%
35' RV - 88 campgrounds 42%
40' RV - 64 campgrounds 30%
45' RV - 32 campgrounds 15%
