I swear, this is not a UA post

For several years now (seattle based) I've been splitting my flying between UA and AS, gradually to a lot more AS especially now that partner flights are EQM internationally. Other than the miles I've got to burn in my UA account, I'm pretty much fed up with them. I'll have silver status on UA next year thanks to travel already completed though won't fly them again if I can avoid. I'm already well past gold on AS this year. I will likely clear 90k partner miles on AS this year, but I could also match to gold or earn even higher on another FF program, particularly one that is part of an alliance. I love AS and they're my primary program, but I've got international and domestic segments that won't typically credit so I should look to take the best option with most flexibility.

Who do you use? Why do you use them /as a complement to AS/ over another program?

For me, perhaps the obvious would be AA or DL for the domestic alliance tie-ins. But perhaps since I'm used to *A I should go with the likes of Aegean or LH M&M?