I'd say Bay Hill. You get a phenomenal field (along with the greatest host on the planet), a good golf course and crowds that are not all that overwhelming. You get predictably great weather. You get all of the other attractions available in Orlando, the great hotels and restaurants. It's an easy place to fly in and out of.
The Masters is terrific, but Augusta is a depressing place outside the gates and not that easy to get to.
The Northern Trust at Riviera is a close second in my mind, because you get most of what you get at Bay Hill, with a far superior golf course, but the field just isn't as good, if only because Tiger is unlikely to play.