Distilled water would probably decrease visible vapor.
Thus, PG will give more vapor for a given volume.
With the huge volumes of vapor with VG anyways, it will not likely be a huge issue.
That being said, I would not
vape the normal grain alcohol you get off the shelf in a drug store. It has denaturants added to it to make it toxic, and thus impossible to drink, so that they are not charged with alcohol tax. It's really meant for disinfection, cleaning and fuel only.