Comfort is the key...
What we use as a guide is if we had to stay inside for 2 weeks due to really bad weather how comfortable would we be. Our first RV had bench seats so the only way to be comfortable for long periods of reading or watching TV was to stretch out on the bed. That would work for a few hours. But for all day I prefer a recliner so I would make sure a fulltime RV would have room for at least one recliner with plenty of room to walk by it. A swivel rocker recliner is best choice.
So an RV with a good sized bathroom, shower, and floor space to accommodate a recliner would be my must haves.