It's totally a matter of preference. A lot of people are sensitive to PG, but it gives you a nice raw flavor and a harsher throat hit. I think that VG is sweeter and kicks out a crapload of vapor, but any VG based flavor that's a little dark will clog up your attys and carts, gunk up your heating element coils, and make you have to dry burn really often.
juices like Dekang that are 80%pg seem to work out ok, and kick out plenty of vapor, but they're a little bit too harsh, and juices like Madvapes Top Vapor that are 80% vg really gunk up coils, and they tend to wick in a very odd way causing my ce2 cartos to gurgle, and they don't flow well in regular polyfil carto's.
All that being said, My favorite is 50/50. Perfect TH, awesome flavor, and plumes of vapor. I first made the discovery of 50/50 when I was experimenting, and I mixed half 80/20 and half 20/80 ending up with 5050 and it turned out great. All of the samples I'm getting from FSUSA are 5050 so we'll see how those work in regular cartos and ce2's when I get them in a couple hrs.