JRF-

In my experience, you shouldn't have a problem as a top-tier getting upgraded out of BWI on either DL or CO. I am silver with both and usually get upgraded on outbound service to ATL, CVG, CLE, and IAH.

My thought---and this is JUST ME---I would choose CO with a cnx in CLE, and make DL my second choice. CO web site tries to book everything out of BWI through IAH or with NW, so book direct with CO. DL is not a BAD choice...I have had great experiences with both...but I've had better experiences connecting through CLE than ATL or CVG.

If you're going to be out of BWI a lot, you'll have no problem finding enough WN flights to make your buddy pass requirement.

For my SAN flights, I usually use US and a CNX at PIT and never have a problem upgrading...but I'm Gold Preferred. US is another good choice out of BWI, especially if you do LAX or SFO.

I'd be interested to know what you decide!