I tend to prefer 12-fret, but have had wonderful ukes with 13-, 14- and even 15-fret joins.
The reason I tend to prefer 12-fret is because they often sound more full in tone (not that I could pick 12- vs. 14-fret in a blind sample) and (b) visually, they tend to put the bridge where it is more aesthetically balanced on the top. Often a 14-fret tenor looks out of balance to my eye.