B vs C---leaks, maintenance, quality

One thing that has put me way way off buying a used class C is their propensity for bigtime leaks, and frequent mediocre build quality.

Are class B's generally less prone to leaks? Where are the weak points for leaks? And if they do develop a leak, is there less likely to be damage, or is that the same deal as a C?

Are the sides of a B constructed the same way as a C?

Is build quality & construction generally better on B's than C's?

What are the better quality brands in class B?

I know there are lots of opinions, but some input based on facts & experience would be helpful.

I have a long-term plan to either do a self-build minimalist type B, or purchase a used one that has been well maintained.