Last August, I have clocked the bus drive time from CBBR to CW, and it was 5 minutes and a few seconds.
We stayed there for 2 weeks, and I can't remember a time when we needed to wait for the bus. Most of the time a bus was waiting at the stop, and when it wasn't there, a bus would pull up into the hotel as we exited the lobby. (okay, we might have waited a couple of minutes on occasions)
Taking the bus and getting to CW took us less time than crossing the road, walking up to SF lobby, taking the stairs down and exiting to the boat dock.
Clearing Security at the boat dock can be done while waiting for the boat, but hardly takes less time than clearing security at CW (and if it's a busy time, you're not even guaranteed to be able to board the 1st boat in)
bottomline, we were already on the moving walkways at CW before we would even have had boarded the boat at SF.
Factor in the time on the boat, and, well ... I guess it would be a tie, or even a win for CBBR bus.