They do sound the same when not using any kind of EQ (Auto Room EQ, Manual EQ) or DSP. Don’t believe otherwise.
I used Denon for a long time (AVP-A1HDCI, AVR-5308CI, and mostly the AVR-3xxx and X3xxx series).
Now I use Yamaha (CX-A5100, MX-A5000).
I think if you are only using Auto EQ (not into manual EQ), then Audyssey XT32 is better than YPAO.
If you are into manual EQ (instead of auto EQ), then Yamaha has the advantage because of the nice 7-band Parametric EQ. Denon/Marantz manual Graphic EQ is useless.
Gene uses the Yamaha YPAO, then uses the Yamaha Parametric EQ to fine tune.
I only use the Parametric EQ to fine tune the bass below 100Hz since I don’t believe in messing with the EQ of anything above 100Hz frequencies.
Yamaha operates cooler in temp than Denon/Marantz. So definitely get an external fan for Denon, but probably good idea to get fans for everything.
Yamaha is supposed to be more reliable and more HDMI-compatible than D/M, according to our local insider guru (M Code).
But in terms of pure Auto EQ, I think Audyssey XT32 is better than YPAO.