I had a 28 foot Class A before doing a significant "downsize" to a 17 foot TT.
The Class A was roomier, but some of that additional space was inefficiently used in the driving area - which really can't be used for much else except seating.
The driver's area was also cold and drafty in the winter time, due to the difficulty of installing adequate insulation and gasketing in all the surfaces around the engine compartment immediately below it.
The TT is definitely more airtight, even though it is single-wall molded fiberglass, without a separate layer of insulation.
For ease of maintenance and repair, there is absolutely no comparison - Keeping the running gear working on the TT is a trivial job.
A pair of top-quality 15" tires for the trailer is under $300.
A set of 6 top-quality 19.5" tires for the MH is well over $3K.
Fuel economy of the Class A (towing a compact pickup) was 5-8 MPG.
Fuel economy of the TT (being towed by a mid-size pickup) is 15-17 MPG.
I will never own another Class A.