Which additionally benefits are you asking about? I believe most of it would be covered from buying first anyways?
Based off of
Alaska and
AA earnings charts, you would get a bit less EQM booking the AS flight directly (1.5x EQM for AS vs. 2x EQM for AA codeshare). Regarding EQD, the AS ticket would be based off of mileage, so you would get .30 * 1024 = 307 EQD regardless of the price paid. The AA ticket would get the fare w/o taxes which you can normally see on the site when booking.