A friend of mine who is a custom installer/ dealer also seem to prefer Yamaha over Denon & other makes.
But I love Denon Audyssey Dynamic EQ, which is not the same as Yamaha Adaptive Dynamic Range Control.
He sounds like a genius!
But seriously, having used both brands extensively (as well as Marantz, Pioneer, Onkyo, & Elite), I would like to add this:
All of these brands have taken their turns at the top of the "Receiver Hill" over the past 15 years or so. They constantly one-up each other and are in a revolving state of cutting to the front of the line. Today, in 2014, I think that it really comes down to the price point (model), required/desired features, and a few other preferences. Some quick bullet point notes....
- At the entry level (sub $650) I prefer the Denon or Marantz gear, although I have not tried the new Yamaha RX-S slim-line piece yet which is priced around there. That being said, the Yamaha product across all price ranges have been absolutely bullet proof where I can not say that about the other brands (in particular, Onkyo - which has gone so far down the hill the last 3 years I can't see them climbing back up again for a while).
- Yamaha's AVENTAGE receiver line I find to be, from top to bottom, a really great product. However, the higher priced RX-V product is similar and just void of some features custom installers would find useful. One gripe is that Yamaha decided to go with all on-screen programming, which can be a pain during initial setup depending on the install and where the equipment is located.
- The amplifier sections in Yamaha AVENTAGE product (and lower depending on the model) can handle 4ohm loads easily. This, to me, is important and speaks to the build quality of the product. Denons typically can as well, but they can run hot. Marantz: I wouldn't try it. They used to be fine with 4ohm, but I have had bad experiences too many times with the last two generations of models.
- Yamaha has the best app in the business. It's incredible, really.
- YPAO or Audyssey? I don't use either (for several reasons) when it comes to receivers so I am indifferent there.
The lineups between the two companies come down to very small differences unless you get all worked up over calibration softare. Not saying your're wrong if you do, I just don't. I prefer the current Yamaha product over the others, but two generations of product ago I would have cursed it to hades. Someone at Yamaha woke up and decided to stop making product just for Best Buy margins and price points and to start making great electronics again.