OP....don't know if you decided on anything yet. But, I've owned multiple Pioneer Elite SC AVRs and currently have a Denon 4311 (predecessor to the 4520).
Really, you can't go wrong with either. They both sit at the very top tier of any AVR, from any manufacturer, at any price.
As was pointed out, the Denon uses XT32, which I find works very well, particularly given my 2 subwoofer layout. That said, my experience with Pioneer's SC series really points out how well they do the amp sections of their top end AVRs. They are really dynamic and, for lack of a better term, "smooth" sounding. They will take a bit of tweaking given MCACCs stubborn lack of subwoofer room correction, but it can be done. One caveat, not sure what version of MCACC Pioneer is now using. The last experience I had with MCACC was probably a couple of years ago. But, they don't change it all that often.
No bad choices here. Good luck!
Music so high you can't get over it....music so low you can't get under it!