By concidence, I ending up camping next to RevLoc Dave last summer at the Six Days of Michigan ride. Had a chance to ride a lot of single track with him, and test out a CRF250X RevLoc he had with him. I ended up with a RevLoc on my 200 EXC after that week, if that gives you any indication of how much I liked it.
I don't have any experience with Rekluse or EFM, so can't comment. But here are my thoughts on the RevLoc implementation:
1) The RevLoc design has been around for many years, and has been refined several times based on long-term testing out in the field.
2) Installation is a piece of cake - basically a drop in replacement for the OEM core. No messing around with filing, shims, spacers, washers, gaskets, measuring, etc.
3) The engagment is perfect, and always smooth, whether slipping the clutch, or grabbing instantly with a quick jab of the throttle.
The RevLoc website is dated to be sure, but the implemenation is awesome!