Well, as a qualified Yamaha Nut and Addict of sorts (although in my case I just have a fetish for 90's Yamaha gear
), I'd say go for the Yamaha being my nuttyness. But.... let me keep going before you take that answer
Build quality on both receivers should be about the same. However, my observations have been (with the lower end receivers anyways) that lower end Denons look cheaper than a comparable Yamaha. However, you start getting into the model range you are looking at, and the cheapness factor goes away.
The Denon has Binding Posts for the Zone 2/3 back whereas the Yamaha does not. Denon also has room-to-room remote, an easier scheme for the composite hookups, and it's made in Japan. To me, those are big pluses.
However, the orange Yamaha Display makes it easy to read at night, and the Yamaha has one more TOSLINK input. The Yamaha remote (I think) is better (be less likely to break with no touch screen), the faceplates that Yamaha makes are something they like to pride themselves on (they usually make everything solid aluminum, even the volume knobs (save for the lower end series)).
So, if you don't care about a touch remote, Zone 2/3 binding post construction, or Made in Japan (which I cannot verify if the 1900 is made in Japan) go for the Yamaha.
The Denon will be a better choice if you are looking for a long term hub in which to deal with as much as possible.
