Unlike my last Buy This, Not That post, I actually like both of the high-end and drugstore products - it is just a matter of price difference here. More info, a comparison, and an ingredient analysis after the jump!
Ingredient analysis (a.k.a chem nerd party):
Red is for shared ingredients
Green is for shared ingredients in different positions
Blue is for Urban Decay only
Purple is for Milani only
Isododecane, Cyclopentasiloxane, Disteardimonium Hectorite, Trimethylsiloxysilicate, Polyethylene, Trihydroxystearin, Triethylhexanoin, Isopropyl Lanolate, Sorbitan Sesquioleate, VP/Eicosene Copolymer, Dimethicone, PEG-40 Stearate, Propylene Carbonate, Phenoxyethanol, Synthetic Beeswax, Propylparaben, Methylparaben, Butylparaben, Ethylparaben, Isobutylparaben.
May contain: Mica CI 77891 (Titanium Dioxide), CI 77491/ CI 77499 (Iron Oxides), CI 77163 (Bismuth Oxychloride).
So what does this mean? Well, these two products have a lot of similar products high up on their lists and other shared ones scattered throughout their chemical make-up, meaning that they're quite similar. If anything, the Milani one just has more fillers in it and more tacky or sticky substances in it.
Chemically speaking, these two aren't dupes, but they're similar enough, perform just about the same, and have just about the same sheerness to them that I probably wouldn't know the difference if you gave me one over the other. If you want to drop $20.00 on the Urban Decay Primer Potion, be my guest! If you don't have a spare Jackson laying around, opt for the cheaper and equally good Milani one instead.