Originally Posted by
tcuhrc
I would still argue that if you book in advance and are somewhat flexible it's easier to get I space on AC than UA.
Redemptions via UA can be freely canceled by anyone, so if you book far in advance and an award drops in price, you can cancel and rebook. That's one of the very, very few advantages of dynamic pricing. However, redemptions via AC, unless you're SE, don't offer such an opportunity.