reviving an old dead thread!
my 95 miata has a torsen, and i wish it had a 1.5 way (mine is a type 1/ 1-way diff)
I've driven both open diff cars, and cars with LSDs. I can say that the lsd for SURE helps keep the power down. (until you lift a wheel with a my torsen anyways)
the only thing i have against the 1 way is that it locks HARD and quickly. It creates an oversteer situation when I want, but I have to keep the throttle mashed, otherwise i get snap oversteer even if i don't lift completely. I think this is due to the torsen unlocking, and also due to the tiny wheelbase.
I would opt for a clutch pack 1.5 way with custom lash and backlash settings if possible.