I do know our choices narrowed down to the 3850 vs 3725 when looking. I'm not sure why but the 3725 has the heaviest published pen weight, but there are others that have a slightly heavier overall weight. My approach to the issue would be to measure the overall coach from the outside at the widest/longest points not including hitches or awnings, then the slides from the insides. As the differences could be a very small amount of sq. ft., a consistent standard of measurement would be important. I do think we all just have what we have, and really its the floor plan, fit and finish, along with electrical and mechanical fixtures and furnishings that seems to attract us to particular models.