I like the XLT standard seats in my 2013 E-350 van better than the Winnebago-supplied seats in my 2004 motorhome, because they fit me better (I'm short) and provide more back support. The seats in the RV are OK, but the seats in the XLT-trim van are better.
But what works for me might not work for you. People come in all shapes and sizes and fitting a seat can be harder than fitting a shoe or a pair of slacks. There are a lot of aftermarket seats out there for vans, as well as OEM seats that work quite well for some people, but you need to personally try them out.
This is not easy, the finding and the trying. Over the years I've sold, given away, or just quit road tripping with half a dozen vehicles because the seats that felt fine on a 30 minute test drive and worked out fine for short trips around town turned out to be back killers when sitting and driving for stretches of four hours or longer. The experience has taught me that seat height and length are critical, as well as being able to adjust for an upright position. Legs stretched out, slouching, slightly reclining all cause back problems for me. Soft springing doesn't work because it means slouching. Best seat for me is a straight-back wooden kitchen chair with a short seat, hard to find that in a motor vehicle.
So I am getting better at finding seating that works. The more you understand about what you need, the less likely you'll get something that doesn't work any better than what you have.
Tom Test
Itasca Spirit 29B