PG, or propylene glycol, is the most commonly used liquid. It has a longer shelf life and produces a stronger TH. It also tends to be thinner than VG.
VG, or vegetable glycerin, is not as widely available; but it produces more vapor, a gentler TH, and stronger flavors.
Many folks these days use a blend of the two; but for the minority of vapers who have adverse reactions to PG, VG is their best option.
If you are accustomed to 100% PG juices, you may wish to try 80% PG to 20% VG and see what you think.