I'd go with Mypoints since they are having the double points promotion. Make sure that you order early since the fine print states that the order must be SHIPPED by September 15. If it's not, you'd still get the 2 points per $1 spent. I've found in the past that Mypoints is alot quicker in payouts then Blink. Make sure you double check to make sure they've given you credit for your purchase. Sometimes I have problems with Mypoints giving me credits for orders. I just send them daily emails until my account is adjusted.
There's a site that compares all the rewards programs called
www.comparerewards.com . The following is all copied from their site.
This is how they say the two programs compare per dollar spent.
Blink $0.000111
MyPoints $0.0071429
So, How Do We Use These Numbers?
So, to find out what a shopping reward of 20 Greenpoints for each dollar spent equals, you multiply 20 x $0.00119 = $0.0238. That's how much you get rewarded for spending a dollar through Greenpoints. To compare it to 3% at Ebates, remember that 3% = $0.03 per dollar. That makes it easy to see which is the best rewards program to shop through for that particular merchant.
In the other example, to find out how much a 2,500 Blink points signup bonus equals in dollars, multiply 2,500 x $0.000111
Hope this helps!