We had a no-slide 28' Class C for over 10 years - during that time we did a LOT of sightseeing which meant we were in a different campground every night. It was incredibly-easy; if we arrived at a location late at night, all we needed to do was throw out the electrical cord. No set-up needed; if it was level enough that we didn't risk falling out of bed, it was good enough...lol! But after spending a month in it during a trip to Alaska, I'll admit that it did start to feel cramped.
As we began to spend more time Snowbirding and staying at a location for a week at a time, we were grateful for our 28' 5th wheel with a single 13' slideout. Compared to the Class C, the 5er felt like a small "apartment". No more shimmying past Ed in the narrow hallway; or stepping over a sleeping dog. The setup/takedown was a bit more "fussy"; but the payoff in space was worth it. The slideout created 2 problems, though: on ours, we couldn't access the pantry with the slide in (duh - the thing that needs to be packed for every trip!); and our heat ducts were covered when the slide was in. For the few nights in freezing temps as we traveled home, when we would have preferred to NOT open the slider, it was still necessary to do so.
IMO, for fulltiming (assuming you are sitting in one place for a while) - slideouts would be mandatory. They make a massive amount of difference!
