Just received my SD blackouts, installation was a breeze, very easy, though they were a slightly tighter fit. I also forgot to put back in some of the rubber padding which would raise the pickup height, so not exactly scientific, but I tried to match gain levels...
My overall impression is that tonally they are pretty much the same. I hear (and feel) a little less compression from the blackouts and they sound slightly more warm and natural, you can hear this especially on the clean pass...