I've been a creditcard user since day dot, game cards never really appealed to me, it really boils down to convenience and time, living in australia convenience probably weighs in more since its not like you can just pop down the road to pick up a card.

The biggest issue ive always felt with prepaid is running out of time mid game, and then having to run out, its not a huge inconvenience but more a hassle, and while im sure its just as easy to manage with prepaid time it just feels like more work, added with the fact most mmo's usually offer reduced prices with bundling, credit card is just feels like the better choice.