Normaly it drives me crazy when people say this but do a search. This topic has been beaten to death. In a nutshell, they are both excellent receivers. I prefer Yammie but Denon is an excellent receiver. Both will do music and movies very well. A lot of people prefer Ymmaha for movies while a lot prefer Denon for music. I thought the Yammie sounded more dynamic for both as Denon is a "warmer" receiver which I do not prefer but a lot of people do. Go listen to them and see which you like. If you do the search you will see it is pretty much split down the middle.
I will say this though, they are both top notch receivers with a high level of quality control. I can't see anyone being unhappy with either receiver. The final decision will always come down to which one you prefer in terms of sound and convinience.