We have had our 24ft with a slide going on 15 years, we have taken somewhere around 15 to 20 road trips from 2k to 6k miles each. To each his own, of course, but we would never go larger, for the following reasons.
1) We are much more road trippers/explorers, than going to one location and staying
2) space, layout, matters much less to us, than the ability to go anywhere
3) we thoroughly enjoy, wondering what's up that road without having to worry if we can turn around.
4) In 15 years, we have stopped at many roadside attractions, restaurants, points of interest, towns, that sort of thing. Where anything larger than a 24 would be much more difficult to park, if not impossible. Even a 26 will overhang you to much, in some situations, where the lots are small and narrow
5) As we do not plan anything, we have always found if there are only 1 or 2 campsites left, we have a 95% chance of fitting. The larger you go that percent decreases
So in my humble opinion, if you are more the road tripper, non planner type, like us go smaller, if not go larger