I don't think there is a right or wrong answer here....
Gift Card - less to carry but a bit slower on checkout
Disney Dollars - just like cash makes the tranaction a tiny bit quicker usually, and if you have young ones it is fun to spend the mickey money !
For my teens, who don't really care about the disney dollars that much, i get them several gift cards for the duration of the trip and spread the dollars out on them equally so that if they happen to lose one.. they don't lose everything all at once. For the two us we just use the Dollars or cash.