hmm, i use a couple different primers for different purposes.
if i'm wearing a mac paint or paint pot, or cream colour base..i always put UDPP underneath OR too faced shadow insurance..
i just recently picked up shadow insurance and i LOVE it, i find it's similar to UDPP but it blends a LITTLE easier and of course, you don't have to cut open the tube to get your moneys worth... so personally i'd say too faced shadow insurance, or of course, a mac paint or paint pot..
i.e; mac paint in stilife or mac painterly or barestudy paint pot...
[sorry for the LONG reply]