I don't think you can do much to west on direct out of BWI. so it is a transfer flight. If the 4 canada prov. are YT, NWT, BC, and alberta, and there is much of that, you will probably need a canadian partner. so you want to choose an alliance that has some canadian airline in it.

US is not a very nice airline at the moment. there Republic partner is much nicer than US.

I have only flown NW once, and found their first similar to that of UA in the two cabin planes.

AA has a nice product out of BWI.

If you will get tickets for F&C travel, consider M&M, as the mileage for premium seats is much higher than in any other program that I know of.

You don't have to fly the program you buy. only the "team"