Please be forewarned, this is going to be the least technical explanation you've ever heard.
What worries me about the strap you linked to is the little lobster claw thingy that grabs onto the plate that screws intot he tripod mount. First, it
looks like it's plastic. Second, it looks like it could very easily be hit and end up opening, causing the loop part of the screw on the connector to be "let go," taking your camera along with it.
(Are you still with me?)
On the RRS strap, the part that attaches to the screw is more like a carabiner. It's metal and there is a special little piece that screws down over the opening portion of the carabiner to secure it while your camera is connected. This way, the carabiner doesn't open up while you are shooting, causing your camera to become disconnected. If for some reason you want to take the body off of the strap...you unscrew the little thing on the carabiner, it works its way up the carabiner so the part that opens is free, and you can remove your camera with the connector still attached.
For only like $15 savings, I think I would probably just go with the RS-4. It really does feel completely secure. I was worried about having my camera dangle from the end of a screw but after getting it all set up, I'm confident I won't have any issues.
Anywho, hope that helps!