There are many AH members who own Marantz, Denon, and Yamaha.
I used to be "all-Denon" for a long time. I had some bad experiences with Panurgy, which is the company that does all the Denon/Marantz repair/refurbish.
After my Denon AVP-A1HDCI died after 8 years, I decided to give Yamaha a try. So now I am on the Yamaha wagon.
Marantz/Denon vs Yamaha?
In Direct/Stereo/Straight modes (not using any EQ or DSP), they sound the same.
You might want to check out the thread about Denon/Marantz vs Yamaha.
https://forums.audioholics.com/forums/threads/denon-marantz-vs-yamaha-vs-anthem-thread.112865/
Short version:
1. I think D/M has better AUTOMATIC Room EQ (Audyssey XT32), but Yamaha has better MANUAL EQ (Parametric EQ).
2. Yamaha probably has the edge in reliability and HDMI compatibility.
3. IMO, the Denon apps (Remote control, AirPlay) suck 100%. Yamaha's apps (remote control, MusicCast) are 100% better.
4. Denon/Marantz seems to have bigger sales and more frequent sales.