Unless you fly a specific OW airline often, AA is most likely the best option for you, especially since it seems you're US-based. Awards are relatively cheap and miles are pretty easy to keep alive with lots of mileage-earning partners as well. You also earn EQMs on AS which is nice.

I'm former BA Silver and CX Gold (currently Silver) mainly flying the Kangaroo Route over the years and even I've been tempted to switch to AAdvantage many times.