If you're cheap, fly B6

If you value peace of mind, fly AA and get the Citi Executive credit card that costs $450 but comes with Admirals Club membership (and you can get 10 authorized users, who also get club access, for free -- get one for fiancé).

When things go wrong, there is nothing better than being able to walk into the AC and have a friendly agent get you on the next best flight option... no waiting in crazy lines, no 2-hour on hold times for a phone call. And the card gets you double miles on your AA purchases and has one of the better trip insurance benefits, which will cover hotel and meals in case you get stuck an night in DC due to a cancellation or something.

Finally (although it sounds like you may care about $ more than comfort), the Embraer regional jets (on AA) really are a nice ride, even in coach. Good seat width, no middle seats, decent overhead bin space. The wifi generally works well too. I did a weekly commute for 2 years on similar planes (E75s) and it was almost enjoyable.