I guessit ultimately depends upon the room you are in and the number of speakers you can accomodate? The Denon is also more powerful so even if limiting the number of speakers to 7 or less, you'd still be better off using the Denon in larger listening rooms.
THe Yamaha is a 7 channel AV receiver with 7 channel processing so can only power 7 speakers and process 7 channels simultaneously. The DEnon is a 9 channel AV receiver with 11 channel processing. THis means that it can power9 speakers out of the box or even 11 if you add an external 2 channel amp. This would allow you to have a 5.1.4 or a 7.1.2 Atmos setup straight away or even a 7.1.4 setup if you add 2 more channels of amplification.