I'm not convinced that any brand has a better quality rep than another - they all have a distressingly high rate of problems. However, some have a better rep for post-delivery customer service than others. Tiffin always gets high marks for that, but Newmar and American Coach rank high as well. I think the best advice is to buy a used $500,000 coach for your $250k. You get better quality materials and components as well as the features and amenities you are going to want anyway, and the bugs will have been worked out. High end models use far better woods, upholstery and floor coverings, design in innumerable features and aids, and usually offer more weight capacity and strength everywhere. Lots of little details that add up, especially for a newcomer who doesn't know much about what to look for.
People tend to think of a motorhome as a vehicle and want "new", but it is first and foremost a "house" and previously-owned should not be considered a negative. Often it is just the opposite.
If you insist on a new one, I would probably be looking at the Tiffin Phaeton, Fleetwood Discovery and maybe the Thor Tuscany XTE. However, a lot would depend on the floor plan and size you are interested in and there are other contenders. Remember, you will get a substantial discount off MSRP, so your $250k budget should buy you a coach with an MSRP of $300k or more.