Okay. These are all popular products that can be used as eyeshadow primers. I own all three, so I decided to pit them against each other and see which one gives me the most bang for my buck.
I used approximately the same eyeshadow application with the same tools, except that I applied Paint with a brush and De-Crease and UDPP with their wands and my fingers. Paint doesn't have a wand and it goes on thicker, so, brush.
For your reference, I have normal/combination skin and I prep all of my eye makeup with La Roche-Posay Active C for Eyes.
De-Crease
Ease of application: 5/5
Longevity: 4/5
Pros: inexpensive, convenient
Cons: not the longest lasting, doesn't help bring out color pigmentation
UDPP
Ease of application: 5/5
Longevity: 4.5/5
Pros: goes on smooth, brings out color pigmentation, convenient
Cons: completely wasteful bottle
Paint (I used a neutral shade since I was just testing use as an everyday primer here)
Ease of application: 4/5
Longevity: 5/5
Pros: pops colors, comes in colors that can further enhance shadow pigmentation
Cons: goes on cakey and dries quickly if you don't apply it very quickly
In the end, UDPP is my go-to choice on a regular basis, De-Crease is what I take with me when I travel and Paint is what I use when I need my makeup to stay put like holy cow.
PICTURE RESULTS
De-Crease after 8 hours:
http://farm4.static.flickr.com/3271/2843977515_bb9fa2fa85_m.jpgUDPP after 8 hours:
http://farm4.static.flickr.com/3223/2858899725_04ffb8bdba_m.jpgI didn't have time to get a picture of Paint, but I can update with one another day if anyone is interested.