whats the difference between a 2 way limited slip differential, and a 1.5 way???? and who makes the most reliable one?

1 way, only works under accleration
2 way works under both accleration and decleration
1.5way works fully under accleration and partialy under deccleration.

Most RWD LSD's are 2way, and most FWD LSD's are 1.5way.

Couldnt have said it much better than moppie himself.:D