I’m unfamiliar with the Fleetwood but I owned a Thor ACE 27.1 for 3 months. Took a loss and traded it in on a Winnebago Vista 27N. Not happy about loosing the money but very glad to be rid of the ACE. I guess that gives you an idea of what I think of its quality
The Winnebago has much more storage, larger closets, and more kitchen cabinets and drawers sized to be fully useful. The Winnebago tracks quietly down the road; no wandering and wallowing side to side, or jarring bounces over bumps. There is no comparison between the quality. With the ACE I had multiple water leaks, trim pulling off the body, one pocket door pulled off the rollers and jammed blocking the bedroom, and those are just the high points. If you are go through an ACE just for fun try out the throne. Unless you're over 6 feet, your toes will barely touch the floor.
According to the specs on Thor’s website and owners’ manual the ACE has a “Crown Roof w/ Exterior TPO Membrane”. The Winnebago and Itasca have fiberglass.