Not just square footage, but also how stuff is arranged within that footprint. An efficiently designed floorplan will seem to have more room than an inefficient design of the same square footage. Agree there is no magic in going back to a 5er, but for those in 5ers no magic is guaranteed just by going to a MH.
No two RVers use their rigs in exactly the same way, one reason why we have so many choices in types and models. What makes one "better" than another is its suitability for how we intend to use it.
I spent 2 weeks at a CG last summer while the truck was getting a new transmission. Glad I didn't have to get a hotel, but to your point we could go around and around on that all day.
Bottom line, there really is no answer to your question, as the answer is specific to each of us. The only definitive thing that a 5er has over a MH is the high ceiling, and whether you think that makes it "roomier" is up to you. Kind of like some folks like high vaulted ceilings in homes, others don't think it makes the room feel any bigger.