I can't speak on the black bulls, but we flushed to Red Native and didn't really like the calves at birth. But they started growing......and now I'm very, very impressed. Have a fall heifer (perhaps one of the first born in the states; she's over a year old now???) that is really, really nice. Everything is right with her.
The bull calf maybe didn't have as much growth as his maternal sibs, but he has a very soft, easy fleshing look. I think he could be a calving ease deluxe bull.
I would not hesitate to use Red Native again. These bulls were said to be out of phenomenal cows.