I'd recommend AA as well, since I go out of LGA and JFK equally. At both airports, but esp at JFK, the GAs recognize status and treat NY-based elite flyers pretty well. JFK's new AA terminal is a dream, and there is never a line at the PLT check in or security lines there. (LGA... ehhh. that's another story...) If you fly transcon a lot, the AA schedules are very convenient.

That being said, I have non-status membership on CO and DL for the occasional trips to smaller cities in the Southeast (Louisville, Huntsville, Mobile and Pensacola come to mind...)