NARS Smudge Proof Eyeshadow Base

I've really been getting into NARS products recently and after hearing only good things about their eyeshadow base, I decided to give it a whirl.  I've only ever tried one other eye make up primer, the infamous Urban Decay Primer Potion, but found it did nothing for me - if anything my eyeshadow slid off faster with it than without.  Needless to say, I was skeptical but I went into Space NK before holiday and caved. 

The product itself looks the same as the UD Primer Potion - it comes with a doe foot (always thought that was spelt dofer) applicator and the product itself is a white, silky base.  While Urban Decay wins on price - Primer Potion retails at £14.50 whereas NARS is £18 - the results from NARS Smudge Proof Eyeshadow Base were far better than what I had imagined.  

Whilst on holiday, I used this primer, hoping it would help keep my eye make up in place whilst we were out consuming cocktails.  It held it in place well but it wasn't until I was working the other day that I really noticed how great this product was.  It was a humid British 'Summer' day and I was hot and sticky and for some reason, that morning I decided to wear eyeshadow. At around 2pm, five hours after application, my eye make up hadn't budged at all.  I was absolutely amazed, I was expecting to be a creased mess, and there I stood, looking the same as I did before I left - hurrah! Instantly this became holy grail and something I will now and forever repurchase.  At £18 for 8g some may say this is too pricey, but you only need a small amount to cover your entire eyelid meaning that this product will last a long time.  

Which product do you prefer - Urban Decay Primer Potion or NARS Smudge Proof Eyeshadow Base?