Like so many things "tone," you just have to hear it and decide for yourself. I like what 12F guitars bring to the table: extra bottom end, less string tension, big-warm tone from the same-sized body compared to its 14F sibling. But I don't own one for its limitations: I use the upper frets of the neck, and the l like the punch and volume you get from a 14F guitar. A 14F can get more "bold" and "forward" for lack of a better term.
So like any guitar, you have to weigh what you like, what you need, and what a particular guitar brings to the table. If resources were unlimited, I'd buy a 12F, but even then I'd likely use it as the "niche" guitar more than my regular go-to instrument.
Edward