I haven't tried Urban Decay Primer Potion so I have no comparison product, I can tell you only that I love the Two Faced Shadow Insurance. It makes such a difference to prolonging the stay of my eye makeup when I wear it. You only need the tiniest amount for each eye lid and it glides across the skin, smoothing over in seconds. I find it colour matches my skin and sorts out any discolouration of my eyelids up to my brow bone and inner corner.
This is such a lovely product, i'd recommend two faced shadow insurance to anybody that wants more staying power from their eye makeup :)