In the past I have used both Alteon in KSEA and Emerald Coast in KMSP. Both places were very good. The instructor did his homework and was familiar with the profile. Although I do not think it matters that much, Alteon has all Boeing customers in their database and were able to quickly set up the sim to match (engines, airports, etc.). Emerald Coast is a little less expensive and you can not go wrong with them either. They use the Northwest Airlines simulator which of course is not maintained to the standards of Boeing in SEA. The key really is to be VERY prepared before you show up to your sim prep, otherwise you are just wasteing money. The time goes by so fast.
BBB