I compared the AP power cords to others in the same general price range ($200-$300 per four feet). Admittedly, I did this with the other AP cables already in my system, which certainly biased my conclusions.
I was basically at a point where I liked the AP I was already hearing a lot, so (a) the AP power cords enhanced that, and (b) I probably wanted to like the APs better since I was already so fond of their sound.
I certainly respect Audience cables, the most serious other contender, but to achieve the same synergy I would have probably had to rewire everything in the system to AU 24's. I wasn't too willing to do that, especially since there's no guarantee that Audience makes a superior product to AP...I'd say they're very close, and the preference for one or the other might come down to personal taste/"your gear your ear" phenomenon.