"As for COntinental, you are correct getting here from other places is fine, but the only flights out of SEA seem to be to their hubs Houston or Newark. If you want to check, then ask for a flight between SEA and SFO or ORD. All the choices come back going either through Newark or Houston. Great for running up the mileage tab, but I don't think my boss'll like that very much. Honest, I;d love to stick with them,. but that's a bit impractical

So I have done some homework, and really aren't that biased."

That might be the case. Flying to many east coast cities you'll find yourself connecting. Quite frankly connecting out of IAH is going to be no better/worse than connecting out of Dallas for AA and will be better than connecting in ORD for United. Generally, employers want you to book a reasonable priced ticket. They don't usually ask how long it takes. The EWR route has good upgrade percentages and plenty of flights.

That said, you're also ignoring the fact that you can book NW, DL and AS on CO. That gives you the choice of 4 carriers going out of SEA to choose from. Good luck on getting AA or UA to match that. You'll also get opp upgraded on NW and CO and you already have CO status so you won't have to wait. Of course, all of that is probably too inconvenient.

Please also keep in mind that UA and AA really don't value their domestic travllers a lot. Both upgrade you very little. AA has an automatic program similar to NW, but only if you're platinum. UA will upgrade its global services and then mostly sell their upgrades. You'll get upgrade certs for them, but you often won't be able to use them on the flights you want. That is, you might not really care to be upgraded at 7am monday morning, but a nice nap at 6pm on Friday would be great. I usually ended up having them expire. Both of these companies also charge you FULL BAR PRICE + tips for drinks in their lounges. They also make you pay for wireless access. So you pay them ~$350 for the right to get into the place to pay them another ~$20 to have a beer and get online.

Your best choice is either stick with CO or change to NW. The latter has a better program (as an NW elite flying NW you get upgraded a LOT). You even get a chance to be upgraded when flying on a points ticket. Being a member of either lounge lets you go in any CO/NW/DL lounge and you can go in the nice AS lounges while you fly on them.