Between those two cards, I would opt for the dual fan Asrock. It will be cooler, quieter, and may even last longer. It also has more output ports if that makes any difference to you. They are both capable of the same clock speeds, so that isn'y an issue. But the dual fan card will likely do it with less noise and heat.
Of course, check the length of the longer card to be sure it doesn't cause issues in your case.