SimpleSins has got her head on.
There really is no "best" mix, unless you're allergic to PG (which is rare).
Personally, I use 90% PG and 10% VG. I like a strong throat hit, and strong flavor, which is what PG juices do well. However, the vapor production on pure PG juices is lacking for me. So with 10% VG I get that little extra boost of vapor production without losing the strong throat hit or flavor.
Other people have different preferences. Some value the clouds of vapor that VG puts out above all else, and use mostly VG. Former "light" smokers also seem to prefer the smoother hit of VG. Others like 50/50.
You'll just have to experiment with it.
