Cat b model wheel loaders good or bad?

Hey guys, been looking at picking up a wheel loader 920 to a 950 size roughly, and heard that the CAT B model loaders were kind of crap. The other models seems to be really nice machines and run strong and long but the B models are just junk. Was also told by the same people (who have owned the B models) that they have buddies with C models that have 30k hours on those things and still run strong.
Anyone have any input on this?
Thanks! Looking specifically at a 1991 CAT IT14B