Welcome to FlyerTalk, mvc22!

As long as you will continue to have Admirals Club access via a credit card, then I think crediting your flights to, and seeking status with, AA makes the most sense for you.

If you expect to lose credit-card lounge access anytime soon, I would consider:

1. getting a credit card that gives you Priority Pass lounge access; or
2. seeking oneworld Sapphire or Emerald status with a foreign carrier like BA or IB. Such status would give you lounge access when flying AA domestically, as well as free checked baggage and MCE seats. But status with BA or IB would not likely get you upgraded on AA. And BA and IB have their own redemption rates, rules, and fees.