Okay, they both can deal with distance (delay) and levels for all channels. So both work with a full set of speakers, including the subwoofer. But the Yamaha system is limited in its ability to automatically deal with an equalizer for the deep bass to flatten the response. So, this means that whatever frequency response irregularities there are in the subwoofer or its interaction with the room (below a certain frequency, somewhere around 60 Hz if memory serves) will not be automatically corrected. But you will still have whatever bass your subwoofer does in your room.
Now, Yamaha has quite a following in large part because they tend to make trouble-free, reliable units.
If you bypass the automatic equalization of both systems, and do the setup identically, you will likely never hear any difference between a Yamaha and a Denon. But most people, when they compare things, do not set them up identically, and so of course they will then sound different. Imagine comparing two identical receivers, with one where you have fiddled with the bass and treble controls, and the other one you have left flat; you will likely hear a difference between them, but it does not mean that those two identical receivers are capable of different performance.
In short, both are capable of sounding good, and so you should pick based on the price you can get (from an authorized dealer if you want a warranty), the features you want, and reliability. Denon is not bad for any of these, but I plan on sticking with Yamaha.
For the exact abilities of both receivers, you can go to the respective manufacturer's web sites and look at the detailed information there, and even download the owner's manuals (at the U.S. Yamaha site, you have to register to download manuals, but it is free). If registering offends your sensibilities, you can go to
www.crutchfield.com and if they sell the receiver, then you can download the manual from them without registering.
