dict and set variants

[James Hague]

stdlib has three modules each for sets and dicts (key/value pairs):

sets: sets, ordsets, gb_sets
dicts: dict, orddict, gb_trees (and ets, I suppose :)

(BTW, notice the naming discrepancy.  Most are plural, some aren't.)

So, what's the rationale behind three versions of each?  This doesn't appear
to be explained anywhere.  To the best of my knowledge, sets/dict have been
superceded by gb_sets/gb_trees (am I alone in thinking that the names
gb_sets and gb_trees are horrible?).  I'm not sure if there are reasons to
use sets/dict any more (should they go away?).  ordsets/orddict are
lighter-weight modules that just store everything in a big list.  Great for
small amounts of data, not so good when things get huge.

Am I close?