I have a couple of dress SARBs (Not the Sumo/Shogun divers) with the 6r15 and I am pretty happy with the performance and accuracy of the movement.
For me, typically if I leave the watch face up during the night, the movement will gain 3 to 4 secs and once I put it on the wrist it will settle back to +1-2 secs per day. Since temperature has a tendency to affect the accuracy of mechanical watches (Hot weather, watch loses time, cold weather watch gains time), my overall daily accuracy average is in the -/+ 4 secs per day range.
I've got a Sumo (SBDC001). It is the best auto diver under US$1000 IMO. You need to step up to an OS300 or AutoZILLA (ok, they are a little under US$1,000) for a worthy competitor. And even then the movements are inferior (until the revised OS300, anyway, and that might be more than US$1,000). The Ti SBDC007/9 also looks good, but it is not that popular, partly I think because of the Monster-like hands.