No MileKing it wouldn't benefit you unless you were looking at trying to only earn more miles or if you do a lot of international flying that you could substitute AC for your UA flights by routing through Canada. If your goal is to earn upgrades and you fly mostly in the continental US, then UA will fit you better. Also, UA lets you purchase upgrades with miles--AC does not.

Some of the AC promos gave you bonus miles on any Star Alliance carrier while others were only good on AC planes.

As a SuperElite AC flyer, I get lots of free upgrades on AC flights (including international ones) at any fare and have had 100% success. Who knows if they will continue that in 2000?

I keep checking each program though to make sure I am getting what I want. In my case it works out to more miles and all of the upgrades I want on the carrier I fly the most (AC).