The black rapid strap is super strong as are all it's joints. The weakness is that it can slip over your shoulder, I've had that happen, it didn't fall on the floor hard, just slid down, but I like the strap very loose and that's what you get. If you're worried, get the optional version that attatches at two points and you will never have a problem.
Personally I'm a much much bigger fan of the optech system, but that would probably be even more of a liability. The shoulder pad has more grip though on the optech strap.