I see no need for gas cards, as they're not versatile enough and they don't save you that much on fuel.
Our VISA card is much more flexible in that it can be used to purchase anything. For fuel purchases it pays back 5% in points ... that's "5 per cent" per gallon in points ... not "5 cents" per gallon in payback points. I request the points back once or twice a year in the form of a VISA gift card that they send me when I request it. These VISA gift cards can range from $300 to $700 each and can then be used for any purchase that you could use a regular credit card for. (For groceries our VISA card pays back 3% in points, and for everything else it pays back 1% in points.)
P.S. Of course I get the 5% in points payback return at any gas station that will accept use of a VISA card. I'm not restricted to any particular brand of gas at fillup time.