Wife and I have a 40' Thomas. We'll be full-timing in her once she's finished to the point we can move in. We figure there's about 320 square feet of living space (more or less - probably a bit less) and an additional 160 square feet of cargo room in the bays below the floorboards. The cargo bays will house water storage, a Webasto, a genset or two, and other assorted equipment required to full-time. We are selling our 30' Ford B600 to a good friend. We found the B600 was waaaaaaaaay too small for our needs. Lesson learned the hard way the first go-around.
I've driven the vast majority of my 2.2 million miles in 18 wheelers, so size is irrelevant to me. The larger the vehicle, the happier I am.
The larger build room allows us to have luxury items like a full-sized refrigerator, full-sized pantry, washer, dryer, full-sized shower, large closets, a king size bed, a big dinette, a full-sized galley, and many other creature comforts smaller buses cannot accommodate. She'll be comfortable, a bit cozy, but she'll be paid for, and all ours.
Just my two cents.
Firearms stand next in importance to the Constitution itself. They are the American people’s liberty teeth and keystone under independence. — George Washington