I don't think these can even be considered similar products. IMO the stila Shadow Pots are creamier and lighter, whereas the MAC Paint Pots are thicker and a bit heavier. I find the Paint Pots are more useful as an eyeshadow base, rather than actual shadow color. The Paint Pots do have better staying power, but the Shadow Pots are a much broader color selection, or at least there was before stila discontinued 98% of them. Hehe.
I don't think the stila Shadow Pots are good as bases. They're fantastic as shadows and as a secondary base. I find it's necessary to use something beneath them otherwise they crease a bit.
I know I'm late, but I hope that helps.