PG - thin, lets through the most flavor, the most nicotine TH, the most nicotine irritation
VG - thick, dulls/smooths everything PG lets through, makes thicker looking vapor
Most people like blends
The way you vape may limit your PG/VG choices for easy use
Normal atomizer + cart (and/or drip tip on a sealed manual battery) - any PG/VG as long as it flow and wicks at least as fast as you vape it
Tank atomizer + tanks - like 30% or less VG, may work with some 50/50 juices ok
Normal stuffing cartomizers - I think these work best with thin juices, 20% or less VG. I also avoid all juices that drop a lot of flavoring sediment (clogs carto stuffing)
Dual coil cartos - some say they can use up to 100% VG in these. But you cannot use the 1.5 ohm ones on slim batteries and some will only go that low on mods
Reservoir cartos - the same PG/VG types tanks like