This is where the confusion is for me... What's the difference between Yamaha's YPAO and Audyssey?
Audyssey seriously might make double digit technologies, lemme see, 2eq, MultEQ, MultEQ XT, MultEQ XT32, BassXT, Audyssey Pro, DynamicEQ, Dynamic Volume, Audssey DSX. Yep that's double digit, lemme see how many I missed. Looks like there is also something called ABX and Volume Extension, but just a 0.5 sec gander looks like it tells me they are not so much for HT?
So, which one did you want to compare to YPAO?
After you choose one, then you have to be specific with both brand and model, because it is those that really confuse consumers, even many AHers. The implementation in various ways, particularly with the available target curves, and which of those can be chosen with any specific listening mode takes time to learn about (and I think really misleads many people).
If you want to know more about how to get the most out of your Denon, I will send you over to batpig's site. I rarely/never peruse it as I've never owned a Denon processor. He is also always at AVS.
http://batpigworld.com/audyssey.html
YPAO is proprietary to Yamaha. No one else uses it. I think it has the reputation as being the most simplisitic of all the well known "RC" techs, as even MCAAC is more advanced so far as I know. However even MCAAC does absolutely nothing with the LFE, AFAIK, and otherwise only corrects down to something like 63hz. It is the bass/sub/LFE where you really get a lot of bang for buck with Audyssey MultEQ and on up.
Other more advanced RC techs that to come to mind are ARC1 and Trinnov (though recent implementation for consumer products don't seem to be very available and/or reliable from my very limited readings there). You can find ARC with Anthem.
But the fact that Audyssey MultEQ can be had for typical budgets is pretty cool. What does happen sometimes (again receiver manufacturer implementation), is the varying amount of processor power available to get the most out of the tech(s).