The non-pg flavors are more subtle and the juice itself tends to produce more visible vapor though the visible vapor does not seem to be directly correlated with increased throat hit or lung hit so don't think it does.
The main reason for VG based liquids is that some people do not physically handle PG based liquids very well. If I use PG based liquids my throat gets sore to the point I loose my voice and swallowing is painful. Using VG based liquids I do not have these problems.
For this reason my liquid purchases have been limited to JC and Juicy Liquids. Soon to be added to that list will be e-liquid planet why will be carrying VG based liquids very soon

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If you do not have a physical side effects from the PG liquids then there is no real compelling reason for you to use VG based liquid other than curiosity. If you are looking for increased visible vapor then you can simply get some USP grade ingestable VG and add a little bit to PG based liquids. Be aware that cutting down a liquid cuts down the flavor so do it sparingly and you will get great flavor as well as large plumes of vapor.
DW