Hi Terry,
WHF gave good reviews for both of these receivers, but the review for the Denon came out after the Yamaha and it referenced a comparison to the later in which it states that they opine the Yamaha amp to be the better performer.
http://whathifi.com/Review/Denon-AVR-2809/
I personally am a Denon owner, but I know that my 3808 has some better internals that differentiate it's performance to the 2809 (it better!!). But especially the way that the review was written, the impression I received was that if you are looking between these two AVRs (especially if you can get them for within £100 of each other), you really should give them a listen side-by-side. I have owned both Yamaha and Denon AVRs and I find that the two makes tend to have a character to them. Especially when people are looking at the better end of the spectrum some people will naturally gravitate towards one or the other's sound.