We just recently moved up from a 24ft class B back into a 34ft class A. Everybody has their own reasons. What works for one may not work for another. Rather than go to a shorter class C we went straight to an A. We decided that the length was not an issue with an rv but the width was. Since most C models are as wide as most A models we saw little reason to settle for less room in a class C.
We now also tow a toad for local area transport and base camp in the A well away from built up areas.. We much prefer driving a small car in the local area over the class B. The reason is that to go somewhere if driving a class B requires moving your "house" and even a small B cannot be parked everywhere a car can. Yes you can tow a toad with most B models but that rather defeats the purpose.
To be fair, it also depends on your style of camping you intend to do. In the B we moved every day or two and parked almost anywhere, so shopped and saw the attractions on the way in and out of an area. Our style of camping now is to stay in one area for longer periods 2-4 weeks at a time. We really enjoyed the B for that time in our lives, but since we now "settle" for longer periods the class A suits us better.
We did enjoy the fast set up/tear down of the B. We did not enjoy being very cramped up with very limited storage and personal "space" and no ability for one of us to go somewhere without taking the house and family (think wife shopping and you wanting to watch football).
The wife is scheduled for a private, professional driving lesson for the new A so she can be comfortable driving and doing all set up/tear down like she did with the B. We also obviously enjoyed the fuel economy. Two last things to watch for: our B had no insulation at all. Keeping it warm or cool was a real problem. Humidity was also a problem. Ours had a heat pump and we ran it whenever we could and opened windows whenever possible. A B is a big steel can that does not "breathe". I would also be wary of diesel models, mercedes sprinters in particular. The new ones have many, many reports of owners (including us) of lots of "check engine lites" almost all associated with the emission control systems and MB dealers that work on them are hard to find. If I were to buy another B it would be a gasser. Hope this helps.