Everyone has their own experiences, good and bad, with all of these FBO's. But I have to give props to SheltAir. I can only remember 1 time where they didn't live up to their typical high level of customer service, and that's because they were just getting slammed (peak travel, busy day). You didn't mention if you were clearing customs, but if so then it is a no-brainer. The CBP ramp is adjacent SheltAir, and their line service personnel will be johnny-on-the-spot to help with bags.