Capt upgrade at LAA, before and after the SLI, is at 65% seniority . At least at LAA , that has gone from 18-20 years to 16, and will continue to drop . Go with the first to hire you.
Retirements starting next year go to ~450, and increases by ~150 ish going forward , before falling off a cliff in about 5 years
Good luck
Joe