Longtable vs. supertabular: Which is right for which job?

Flippant comment moved to answer as requested:-):

If you use any of the mentioned packages other than longtable then any bug or problem reports don't go to me. That is a definite advantage of using those packages.

which one is the right one (or the better one) for which type of long-table?

Unfortunately, longtable issues a "longtable not in 1-column mode" error message when used in multi-column documents, while supertabular does produce multiple-column and/or multiple-page tables in such documents.

As a side note, on the other hand, supertabular breaks columns earlier than it should (thus leaving partially blank column bottoms). I've also tried xtab, which presents itself as "[...] an extension of the supertabular package and also reduces or eliminates some of its weaknesses." in its documentation, but the problem got worse, since xtab broke columns even earlier than where supertabular did.