I'm in Seattle now, and overall I would probably say Portland. Then again, I'm not much of a city person so that sways my preference.
Seattle has a busier economy, more nightlife, cultural life, expensive real estate, slightly less friendly people, more urban sprawl, more food options.
Portland is a little smaller, more limited job options, cheaper to live there, cleaner, less nightlife, fewer homeless, slightly more sunny days, still a decent cultural and food community.
Both have laid back people, great outdoor activity, healthy economies, access to other cool places to visit, etc. If you want more city, pick Seattle. If you want more local community feel, pick Portland.