With all due respect to AS, they do not have the trans-Pacific flights that have been part of the original poster's (OP's) comment history.
Plus, UA has a mileage-based lifetime (million-mile) Premier Gold status that is well worth striving for.
If the OP is close to Marriott Bonv°y Titanium Elite status, that might be worth getting. It delivers complimentary MileagePlus Premier Silver membership, which means Economy Plus seating at check-in (subject to availability).