Grand design does stuff better, they also do things worse than others. RV's are a mixed bag, they are very similar. Now we felt overall, floor plan and quality that GD was best for us, otherwise we wouldn't of purchased. That said, they are mostly similar for the most part but I'd put GD over some and on par with others.
I would buy a Momentum again. In fact I'd seek out the brand.
I would not buy a DRV again, even pre sale to Thor, much less after the sale.
I would buy a Newmar again.
It's a house that goes 60mph + down the road. You are going to have trouble with it at some point. We are quite pleased with the response we have received from grand design and their willingness to let me fix stuff and just send me a check. They've worked with us on the few minor issues we've had over the last 6 months and I'd buy another one in a heart beat.