The best deal bounces around from lot to lot. I use this site to find the current best discount. I've used them all from time to time, depending on who is cheapest. They're all about the same distance from the terminals. They're also all cheaper than the recently jacked-up $9/day lots at the airport (which are not really at the airport), and the shuttles for all the private lots run more frequently. I've waited waaay too long (45 mins+) for on airport parking shuttles. Never more than 15 mis for a private, off airport location.