Let us compare the two carriers on what it takes to get those “premium” seats at booking.

Alaska:

- MVP status
- 20k EQM miles flown .
- booking in a Y, B or H fare class.


United:

- Premier Gold Status
- 24 PQF and 8,000 PQP
or
10,000 PQP

so it looks like Alaska would provide the benefits cheaper. Alaska has no PQF or PQP. But , as you saw, to get into those Econmey plus seats at booking , there needs to be seats available. Often, people who fly on Alaska, they book the flights months out and rarely at the last moment. There might be a chance seats would open up if those individuals booked into Premium seats are upgraded to First. This would be the same for any air carrier.