I like Park and Zoom, because the spaces are bigger and its closer in, but its a few more dollars per day. I parked at Parking Spot once, and didnt love it, but you can turn into it before you get to the airport. I dont know how they are priced now.
What is the most reasonable long-term and with convenient shuttle?
I have used Fast Park for years, never had a bad experience. I like it is on North side of 71, easy access to get back home in Austin. Access via Spirit of Texas.