i raise pedigree belgian blues as well, and do sompe shows with them. the show quality of a BB depends on what kind of show you want to enter. because they are very different then other breeds of cattle, so other criteria are used to judge them. if you want to, i can send you a copy of the system used in belgium to judge BB's.
their pro's are easy: they give you excellent amounts of muscle, extremely good growth, highest dressing out percentage of any breed in the worlld (72 % average) the nicest disposition that i know of and they are very easy to train for shows or anything. their meat also has very low cholesterol and fat, so it's excellent for heart patients.
cons are that the calving ca go very difficult, so breeding for calving ease, or being willing t perform caesarian is not an option, it's a necessity. this is really the only negative point about them. in crossbreeding i don't know of any serious problems.
some people say they don't taste as good, but if cooked quickly and on a hot fire, i think they taste a lot better.