I've used them both at different times. Signed up for each with different mileage promotions. Services were very similar as far as ease, turn around time etc., but this could vary depending on where you live. Advantage of Blockbuster is that you also get 2 instore movie rentals per month, so if you live near a store it is a nice option (If I recall correctly these, coupons could also be used for video games, so if you have kids that rent games that would be a definite advantage).