I am a 1P on United. Not a 1K, but still a good elite. E+ is United's first class cabin. Alaska is way more liberal on first class upgrades than United. And the service is way better. So that leaves UA elites to settle in on E+.

I agree with Eastbay1K that Alaska isn't likely to remove seats. Bottom line is the bottom line. I don't pay for E+ nor did before I made elite. So if Alaska takes seats out, the remaining seats have to work that much harder. Great if that works, but I don't believe it will and it is a big risk.

Secondly, the 737-800 has a pitch of 32" (source: Seatguru.com). But Alaska has a trimmer seat, which means 1-2" more knee room. United has thick seats on the 757s and so that 36" doesn't get any better. The Alaska 737 is a comfortable plane. Much better than the 757 in E- on United or Delta. Even the Southwest 737s are a comfortable plane. I have found myself on Southwest much more these days.

JetBlue took seats out because the A320 is not a transcon plane and they had to fly empty seats due to fuel loads. Then they realized they could fire a flight attendant and take the seats out that they were flying around empty. They then did the customer friendly thing by spreading the seats out. If they could fly 162 seats, they would.

Remember, at United, if the flight attendant smiles at you, you have reached, "North of Expected." At Alaska and Horizon, a smile is usually just a regular day at work.