I'd say also given your location, i'd also fly/join the Alaska program. Although I'm on American, Alaska does have a fairly extensive partner system, notably NW, CO, DL and AA. The only detriment is that I hear that it sometimes takes more miles to redeem on partner airlines versus on Alaska.

Please note, recently Alaska has had problems with on time performance. Peek into the Alaska Forum and you'll find out more.

Happy travels,
pb