Don't bother with the Discover. Nobody takes it. And even if they do, the card just isn't any good. The discover plat won't back a warranty, the cash to point ratios are not favorable, and it's not worth the tack in your credit.

Mastercard isn't a bad idea - I forget which store it was but one of the huge warehouse clubs only took mastercard. But that's the only time I ever saw something like that.