What's the Best Eye Primer for Different Skin Types?
Using the user ratings for different eye shadow primers from the Makeup Alley website, I was able to work out which primer would be best for different skin types.
I analyzed Too Faced Shadow Insurance, L'Oreal Eyeshadow Base, e.l.f Eyelid Primer and Mac Paint Pots
UDPP vs Too Faced Shadow Insurance
There seems to be a lot of confusion about what is best for oily or dry eyelids. Some reviewers felt UDPP was better for oily lids and some said too faced insurance did this better.

While the results aren't conclusive, this analysis shows that the best eye primer for people with
- Very dry skin - Too Faced Shadow Insurance.
- Dry skin - Too Faced
- Normal - both primers rated the same
- Combination - slightly better with UDPP
- Acne prone - Urban Decay Primer Potion
- Oily skins - Urban Decay Primer Potion.
- Very Oily - UDPP
- Sensitive skins showed a slight preference for Urban Decay Primer Potion.
Urban Decay vs L'Oreal Decrease Eyeshadow
The L'Oreal analysis is based on only a small amount of reviews - 94, while the Urban Decay Primer Potion had 4,316 reviews (as of 17th March 2011). I don't know if this is because it's a less popular product, or because users of the Makeup Alley site don't use drugstore makeup so much.

The analysis showed UDPP was much better for all skin types except sensitive skin (only based on 3 L'Oreal reviews) where it had the same rating.
I was a bit surprised the L"Oreal product was so badly rated, many of the videos felt it was a good cheap substitute for Urban Decay Primer Potion. There you go, better to check out the numbers that any one person's opinion I guess.
Urban Decay Primer Potion vs e.l.f Eyelid Primer
Once again, the e.l.f. analysis is based on only a small amount of reviews - 100, while the Urban Decay Primer Potion had 4,316 reviews (as of 17th March 2011). I don't know if this is because it's a less popular product, or because users of the Makeup Alley site don't use drugstore makeup so much.

It is difficult to draw conclusions with such low numbers of review. People seem to be happier with this product than the L'Oreal one. Seemed to stack up OK against UDPP for dry and oily skin types, but the number of reviews for these was very small - the ratings were lower where there were more reviews (for normal and combination skin types)
Mac Paint Pots
There wasn't enough reviews to make a good comparison here. What there was was very positive over most skin types.