We've owned our B for almost four years and had some of the best travel experiences of our lives.
Not long ago, we saw a friend's new small C with a living room slide that really opened up that space. It looked very tempting, and I can see going to a small C Sprinter eventually, now that we have a big black dog taking up some of our space.
Meanwhile, though, I keep remembering what I love about the B. I really hate to give this up just yet.
1. Miles per gallon. We plan more cross-country, two+ month trips.
2. Car-type driving. Every time I read on RV net questions about "scary" roads, tunnels, mountains, etc at places we visited, I remember we had no concerns in those locales. Friends in a small C did not enjoy some of those same scenic roads.
3. Parking. City streets, tiny towns, our driveway, any RV sites anywhere, easy.
4. Quick set up on arrival, and pack up for departure from campsites. This goes VERY fast for a B, which makes one-or-two night stops so easy on long touring trips.
5. Double duty. We use the B as our second vehicle at home because it is parked beside our garage. (Our neighborhood by-laws allow vans but not RVs.)
If it helps the OP - I'm glad we got the B first. We've never regretted our choice, and love our diesel Sprinter. Going to something bigger is always a possibility later, and the resale market is very strong for class Bs.
LTV makes top quality products and the Serenity is beautiful, though I'm also not a fan of corner beds.
If I were giving up some of the car-like benefits of a van, I'd be looking at a small C with a living room slide where the sofa goes out, to really open up that evening space. And I'd either get fixed twins (make up the beds and leave them until sheet-changing time) or a rear-slide walk-around queen bed.