I have miles in both accounts. UA awards beat ACs in many instances. But fuel surcharges make using the AC miles impossible in some instances.
You should try to accumulate in both programs, AS LONG AS YOU STILL QUALIFY for GOLD in ONE OF THEM. After being 1K for the better part of a decade, I think star gold is enough. AC's gold gets you worldwide lounge access on everyflight. UAs excludes the lounges in USA for domestic travel. But, with AC gold you cannot get E+.
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