Stylistic advantage to Diaz imo. Though Jorge is a good wrestler in his own right, he doesn't use it offensively, which is Diaz' glaring weakness.
A majority of this fight will take place on the feet. Nick is a WW who has fought at MW, while Masvidal is a LW who fights at WW. Both have similar skill sets with their boxing. Jorge employs more of the slick Cuban style, while Nick prefers to drown his opponents with is high output.
Should this fight become a boxing match, I believe Nick wins that 10/10 times. He's just to tough too be hurt by Masvidal. Masvidal will succumb to Nick's pressure and get tko'd.
Then again Nick's been out forever and has been drinking heavily. So who knows. Maybe I shouldn't be speaking in absolutes.