I know that 4 months ago when I wanted a new reciever, I bought a brand new Marantz SR5007. I had it for 3 days and returned it for a Pioneer SC-61.
I personally believe MCACC to be much more capable. This is just more opinion than anything. But I found that audyssey just lacked something. Plus, when I run audyssey, it's just a simple few chirps in each speaker and it's done. MCACC runs all sorts of various tests. It lets you customize your sound much better. More options. Whether it's front align, symmetry or all channel adjust...or whether it's your delay time...or whatever. Everything is fully customizable. You can tweak EVERYTHING.
I played around with Audyssey a lot in those 3 days and I found I couldn't tweak as much as I'd like. It seemed to me that it was more designed for the plug and play person.
Again, these are just my personal opinions and observations.
If your a guy that likes it to be complex and a guy that wants to have total control, go with MCACC and a pioneer Elite.
Plus, I found the Marantz ran extremely hot compared to the class d of the Pioneer Elite. My elite only gets warm after some heavy extended use. As Catbrat pointed out, I also found there is a lot more heavy end, or "chest thump", after running MCACC compared to Audyssey...and I like it a lot!
I would have typed this all up the first time, but was on my phone