Actually, post-Crisis Legion wasn't much different from pre-Crisis - just a few tweaks here and there to downplay Superboy's and Supergirl's role and to add a couple of retroactive new members. Although I suppose the Legion currently on show in Action Comics is a sort-of pre-Crisis Legion that developed on a different time-line from the one shown in the late 1980s - i.e. no Five Years Later storyline.

The other Legion is the post-Zero Hour Legion that was rebooted in 1994 and lasted about 10 years. This has often been referred to as the "Archie" Legion for it's light nature.

So I suppose there are four Legion continuities.

I think I'll stop now before I confuse things even more.