need help with purchase of new bunkhouse

TPO roof is fine. Ask the thousands of us out there that have them trouble free for decades. Fiberglass is great until you have to fix it (TPO is easy to fix). They all have seams and holes no matter what roof you have and that's where an issue will be, not the roof material. This would not be a deciding factor for me. All have the F53 chassis and all have the same components. Quality, for some reason Winnie is held in regard as the Apple of the RV world and frankly after walking through some at a local dealership the quality was the same as anything else you'd walk through. Plastic faux metal faucets, veneer luann cabinet side panels, rippled wall seams, same slide mechanism etc. The only thing higher end on a Winnie IMHO is the price tag. Not that the Thor Miramar is better, it's just not worse than the vista. Frankly I walked through a lot of gassers from every manufacturer and they are all the same quality - including Newmar and Tiffin. I challenge anyone to walk into several rigs ignoring the badge and tell me what brand you are in. Pick the floorplan you like. Despite the brand bashing you hear, many of us are very happy with our Thors and their stellar customer service. I would caution one area; stay away from a full wall Schwintek slide. The system is just too weak to handle the big slide and you could have problems. Other things to consider, weight and tow weight, wheel base (longer is better), tank sizes, if residential refer then battery and inverter sizes, slide mechanism (mentioned this already), seats - I know this is crazy but you will spend a lot of time in the driver's seat, I have found on some really higher end rigs the seats just weren't comfy - not that they were bad per se, just didn't fit me. You need to find the unit that fits you, spend less concern on brand and more on layout and what you want. Any brand will be fine and will support you, sans some things to look for.