PG is thinner, carries the flavor better
VG is thinker(lot thicker), mutes the flavors, produces much better vapor, is more natural some even "organic".
Some people have allergic reactions to PG so they will go with VG but based on the studies I'm seen less then 10% of the population has this allergy.
If your not allergic or convinced your are....most folks recommend staying in the 10-30% VG rest PG for the best taste and vapor.