Personally for me the best two choices are AA and DL simply because having a club in my home airport is always a huge plus. Now, with the club being important to me, DL scores more points with free booze in their clubs (;)), plus you get unlimited upgrades. They have been using a few 737-800's in all coach (with increased seat pitch though) into here, which kind of sucks, but there's less now than there used to be at least.

The downside with DL is the RJ's ...