The other option to consider is simply having
www.diffsonline.com build you a customer LSD for the specific use you have planned. You can choose something like a 3-disc setup with ramp angles to give you the aggressiveness or lack thereof on acceleration and deceleration. You could also choose to go with a wavetrac, quaife, os giken LSD designs if desired. Don't underestimate the resale value of the diff when you're done with it also. If it's in good shape in 2-3 years, you can probably get about 60-70% of your money back selling it while in the meantime enjoying exactly what you'd like to have.
disclaimer: I have no connection with diffsonline other than selling them an E39 M5 diff years ago (my M5 LSD discs gave it up by 50k miles, so I bought a new one from BMW which I got an incredible discount on at the time) where I found Dan excellent to do business with, so I'd use them again in the future.
To answer that question about the E9x M3 and E6x M5/6 LSDs -- those are viscous action LSDs with lockup varying from 0-100% based on load and slip. On corner entry (deceleration) they are open, 0%, so no corner entry to apex pushing. The "issue" some have with these is that they require slip to have started to begin to function, but I will say that it works right away and is very progressive with load (power). My jury is still out on my overall opinion of it, but I think you'll find no racer would care for the design -- they would much prefer an "old" Salisbury LSD with proper ramp angles for load/unload they want and the static lock they desire in order to give a more predictive and functional solution on track.
I can say that comparing the E90 M3 LSD and the one in my E39 M5 (which btw is stock, 25% Salisbury LSD from BMW like the one being discussed in this thread), is that for serious driving on R-comps, the M5 diff is too weak. It needs much more locking on acceleration as the torque of the S62 can still spin the inside tire too much on corner exit on something like NT-01s or Hoosier A6s (hence the reason I wore out the discs in my unit by the time I had 50k miles on the car
). When I back-to-back these cars, I can tell right away how the M5 diff is allowing too much inside tire slip when powering out of a 2nd gear corner for example. The M3 feels more connected and can really put the power down on corner exit.
Regards,
Chuck