Part of me has this urge to convert a 12-string guitar into a triple-strung bouzouki, with a single high octave string on the lower courses and a single low octave string on the higher ones.

GgG DdD aAa eEe

With eight strings, unison every time for me, there are no strange jumps in fills and melody lines as you cross strings. I don't particularly like the wash of poorly-defined sound you get from a 12-string guitar, either.