As stated 19.5 you get a spare. 22.5 you don't (Generally)
Better ride, More ground clearance. HIGHER PRICE.
But I'd not want 19 inchers on my RV. I'm very happy with mny 22.5's
And as for the spare...
I helped a friend change one once. I'm a big and fairly strong dude (6;2 cand lift 250 pounds) and loading that flat into his pickup.. That was right at my limit. I'd not want one pound heavier. In fact that was like 7-9 years ago and I'm not sure I'd want to attempt it today.
So a Spare would not do me any good. Just be one more tire to replace.