you should also consider signing up with Hilton HHonors as well. Whatever the FF program you choose, HHonors will likely help you earn miles quicker with their Double Dip feature, where you'll earn 500 airline miles for each stay. Not only that, HHonors will also allow you to EXCHANGE your HHonors points into airline miles, and vice versa. Now IMHO there are so many ways to earn HHonors points, you'll be getting free airline tickets or hotel stays in no time.