None. There is no difference in real world photography.
I've seen an example where someone shot an image 6 shots underexposed then raised it + 6EV in raw and had slightly more detail, but in reality there is no measurable or noticeable difference between 12 and 14 bit. In other words.. 14 bits sounds nice for marketing, but no one can see a difference.. its a "feel good" but invisible feature IMHO.