This is probably not going to be any surprise if I say that the best primer is the Urban Decay Primer Potion, followed by HEMA eyeshadow base and then there are NYX and NYC, but you can pretty much put them together in the third place. I have to stress though, that there is a huge gap in quality between the second and third place :-).
Primer Potion has a light consistency, it dries invisible into your eyelid and it makes the eyeshadow last all day long. HEMA eyeshadow base has a creamy white colour and it does not blend that well into the eyelid, but your eyeshadow will not move one milimeter, that is guaranteed. NYX eyeshadow base has a very disappointing performance, it starts to melt about 4 hours after you put your make up on and NYC has about the same longevity. They are both of skin colour and have a light creamy consistency.
|From left: violet eyeshadow from NYC palette, HEMA, NYX, Urban Decay, NYC.|
I swatched all bases: first is an eyeshadow on its down (left), then HEMA, NYX, Urban Decay, NYC. Top row is a base on its own and bottom with the eyeshadow. Now it is also perfectly visibly why it pays off to wear an eyeshadow base, the eyeshadow colour just pops out!