I know which Cain (Wolf Performance) prefers for traction

To be fair the SSL version is technically superior but the MMC version has the link mountings welded to the back axle. It does benefit from the addition of SSL dual rate coilovers though.
I've also heard from more than one source the SSL 5 link kit has too softer springs. I believe Peter (Gambalunga) asked for higher rate ones for his car.