My answer is none of the above. Join NW's program and you can fly NW, CO, DL or AS out of PDX or SEA. True, if you're down with the Eskimo, you'll get upgrades on AS, but when you fly others you won't.

With NW, you'll get a good upgrade percentage and get upgraded on CO's flights. With 75K miles you'll also get platinum, which offers other benefits such as increased award availability, 1k free miles when you don't get upgraded on NW, etc. Basically, you'll get upgrade more on the things you fly.

The AS value proposition might be close, but the AA one isn't.