get the Deluxe if you can afford it.
Im guessing it's a Precision bass you're after?
if you get the Standard version, you only get one pickup.
the Deluxe version has one Jazz bass pickup and one Precision bass pickup, so it's more versatile and better sounding. I think that's the setup Duff prefers.
have you tried them?
www.sound1.no has pretty good info on them.
oh yeah, the difference between Mexican and American is that the american is better, simple as that!
the Mexican is about halfway between the Squier and the American series.