In a bull....on heifers, I prefer that they have lighter bone structure. In my mind, a live calf is better than a dead calf or one I have to assist. And better yet, if they can gain as good or as close to the rest, so be it.
On my cows, and I am an Angus breeder, I would prefer they have a little more bone. Foot angle and leg structure are still a major factor when buying a bull.
I don't think that calf buyers are looking at the amount of bone in a calf compared to the weight of a calf, at least around here. The feeders and buyers around here are still concerned about the price of gain, so if the calves weigh what they should, they will take them, except for rat-tails.
When we shipped our calves last fall, it didn't really matter how they were structured, it mattered what weight group they fell in.