Ok,
I really don't know anything about the BM tranny one at all.
I guess the Phantom seems like a good deal, b/c it is cheap compared to a Quaife or Ralliart one. But the Phantom Grip isn't a true LSD like those, not saying it doesn't produce similar results though. And I have no idea if it will make your diff. stronger or not. I would say, check in the Gen Tech, as I am sure there are some turbo guys that have done one or the other, that have a ton more knowledge than myself. Good luck, and post your findings here, as I am sure many are curious about this.