Motorcraft...on my GT I have a Purolator, Advance didn't have a Motorcraft piece. Not gonna be a big difference here with brands...
And 15k for a fuel filter is too often. Not necessary to change it so frequently. I'm pretty sure Ford calls for it at every 60k.
Edit: Unless the filter is causing restriction in the gas flow, you won't notice an increase in MPG when replacing it. Older engines get worse gas mileage than when they were brand spanking new. This is just reality. Sure, there are tons of things you can do to help keep it up, but the main thing is you right foot, unless there's really an issue someplace. Just don't expect 39mpg....I had to.