Why only one? Is this your last marathon?
[Disclosure on my perspective:
1) I'm a 2:50-3:00 guy; not as fast as you
2) I'm in CA, so my experience is West-Coast-weighted
3) I've run about 45 marathons
4) I'm an old(er) dude , so I sometimes pick races that I can compete well in the 50-55 AG ]
Boston: (Run it 8X) Best experience [but, I see you've done it enough]
CIM: (8X) Flat-to-downhll. Mostly, good weather. Excellent organization. Very competitive for it's size. Big enough to have an expo and crowds (when you get to downtown Sac) but small enough to get a well-placed hotel.
Chicago (5X) Flat. Nice logistics (loop course, near hotels, subway). Competitive, so good chance you'll have someone to run with. Good travel destination.
St George: (2X) Huge downhills. Great weather. Very good organization.
Napa: (4X) Beautiful, fast, net-downhill course, similar to CIM. Smallish, but you might contend for a top 5 place. Lonely last few miles. Good place for a post-race vacation.
Houston (1X) Flat course and usually good weather. I think you still finish with 1/2 marathoners (at ~2:40, there are a lot of them in the way).
NYC: (1X) Great crowd support. Wonderful trip, but not a fast run (in addition to the course profile, I had too many dinners/shows/sight-seeing excursions)
SF: (3X) Not fast. Very early start. One of the few cool-weather races in the summer. Lonely last 6 miles.
I'm curious to hear which race you pick and how it goes!