I understand how you feel because it took two years for us of considering every option before we bought. It gets overwhelming and you hate to commit to the wrong thing.
We (two people) travel the way you describe, long distances mostly in the summer, three to four months and about 10,000 miles a year.
The used Sprinter diesel Class B we bought three years ago was in your price range, and you mentioned possibly considering a B. The smaller interior space is not for everyone (that's the potential minus), but we found a B to be ideal for the way we want to use an RV at present.
These are the pluses from my experience:
Fuel mileage in the low 20s or better per gallon of diesel, depending on how fast we drive. We have about a 600 mile range between fill ups.
We do not need to tow a second vehicle behind.
Virtually any campground can accommodate a class B van RV.
Signs that read "no RVs" for certain roads, parking areas etc, in National Parks and other locations are not a concern - on asking, we are told, "Oh, you're OK," and waved on in.
The smallest tunnels I've ever seen (in South Dakota) were not an issue.
We have everything (food, water, bathroom, change of clothes) when out sightseeing.
At home, we can park it in our driveway, very convenient, and use it for hauling, too.
The turbo diesel engine is a workhorse that never breaks a sweat in the Rockies.
The set-up on arriving at a campground takes only a few minutes to check the site's level situation and plug in the electric cord if there is power at the site.
Departure is also very quick. Unplug, fill up if you need fresh water, dump the holding tanks if they need it. Hit the road.
Cleaning our "home" on the road every week or so on long trips takes just a few minutes.
Class B vans have an excellent resale value, especially diesels.
Canadian companies pioneered the van conversion market that exists today, and you could visit a factory or two. Layouts vary - some are more open than others, giving more visual space. Interiors often are hand-fitted with top quality solid wood cabinetry that holds up extremely well.
Feel free to send me a private message if you have questions about B type RVs.