I've flown them all, and NOTHING beats United PS! You will find the best seats and service in all classes. Personally, I would recommend Business -- the seats are comprable to that of American's first-class domestic first, and yet are less expensive. First of course is great, however I don't see a huge difference between PS first and PS business.

You will recieve better service, better food, a better seat, and not to mention... you will get a DVD player with 10 new release DVDs to view during the flight (Fox's "House" is always one of them). Try it out, you will not be disappointed. Did I mention I have a 90% upgrade success rate?