Heck, I thought you were asking about something else!
OK, Yea RV size does matter. Maybe not so much in private and state run campgrounds, but even in some State parks smaller is better Especially the older ones that have not been updated in recent years. In National Forest parks, especially in the far west smaller is a definite advantage. In the parks where you might have room to park a larger RV the roads might just not support access. 25 feet is probably not a big problem for 99% of the parks, but anything bigger and your site choices go down to practically zero.