I don't think its anything against the Upstrap but a vote for the weight handling capabilities of the Op/Tech. The Op/Tech is made of neoprene which really helps absorb the weight of a heavy camera like the RB. The webbing used on the Upstrap will transmit the camera's weight straight to your shoulder. I find the Op/Tech really helps when walking around with any heavy camera and an RB with a 127mm and the multi angle grip counts as a heavy camera!
Look at the Op/Tech Super Pro strap with clip design "B".