IMO, search carefully and long for a floorplan that works in the 25-30 foot range - compromise may be required. Otherwise, you'll most likely end up having to compromise in other ways: site selection. I have a short trailer, but my parents don't. There are several places I go that they can't, or more commonly, where I can stay in most any site but they're restricted to just a handful due to length.
I'm not very familiar with 5th wheel floorplans... If an east west bedroom takes up more space and runs perpendicular to the length of the trailer, then get the other sort and always drive east or west so that the bedroom runs east west. :)