I PM'd megarat on that. But in a nutshell, I found the white xm to be too balky. Even after greasing the stems. YMMV of course, but I can't really recommend the white xm switches. They start off great and sound nice and loud, but over time my fingers get tired.
This doesn't happen to me on the BS keys, let alone any of the cherry keys I have used, also the topre.