I would suggest visiting an LBS (local bike shop) in your area. I'm sure there are many to chose from in the Seattle area. Both of the brands you mentioned are good but there are dozens of brands that all make equal bikes in the same price range. You'll find that in your price range every bike will come with the same components (Shimano Claris, Sora or Tiagra) and the frames from different manufacturers will be comparable. Different shops specialize in different brands so I would find a shop that has a good reputation and go see what they have in your price range. As a newb, getting a bike that fits properly is the most important thing and if you don't know how to fit yourself that is where the LBS comes in. I am a fan of used bikes since you will get more bang for the buck. Might be worth perusing craigslist but if you buy something that doesn't fit right you'll be unhappy and be selling it in a few months and buying something else