I've been picking tulips forever and with UA and US in the WAS area, *A has been a no brainer. UA hasn't been high on my list for a while, but it was still the clear choice with *A the dominant carrier at IAD and DCA. The (assumed) *A divorce and AA/US merger makes this a very different question, especially with the AS flights outside the perimeter.

Which side would you pick?

AA/US/AS/DCA

UA/IAD