I didn't switch as much as shift. I've been MVP Gold on Alaska (their highest level) for a decade and was Platinum on NWA for only a couple of years. Rather than preferring NW for transcons, I moved those flights to AS in markets where AS has SEA-originating transcons. (I did a NW Plat status match on UA at the same time and never used it due to AS' nice SEA schedule.)

I still fly NW when I have to go to MSP specifically. But, for example, when I have to go to Cedar Rapids, IA, I'm more likely now to fly SEA-ORD on AS and drive, rather than fly SEA-MSP-CID on NW/Pinnacle.

I almost always am upgraded on AS for any flights that are not transcons. On transcons, it's not as often since -- like MSP-SEA NW business-hour flights -- there's a lot of high-level frequent fliers on them. But on AS I don't have to make connections when I fly to BOS, MCO, EWR, DCA, DEN and other non-stop destinations that AS serves from SEA. That, in itself, is a benefit, even if the identical seats are exit row.

Who knows? It may all change again in a year or two and I may fly NW more, depending on my travel patterns.