When I get a job I will also be buying a new Blu-Ray player for the kitchen, and I also am considering between the Denon 2012 and the Marantz UD6006. Throw the Oppo BDP-95EU and the Cambridge Audio 751BD into the mix, and confusion reigns. The group test in the August 2011 issue of What Hifi preferred the Marantz, though it also rated the Oppo and the Cambridge as five-star products.
For me, the two most important things are picture quality and sound qualitiy, with connectivity a close third. Also, they must play SACDs. I am not concerned with smart apps, or even, at this stage, with 3D, though 3D comes with all four players. The Marantz, Oppo and Cambridge all seem to be very good for picture and sound. However, the Oppo and the Cambridge have better connections than the Marantz and the Denon. The Cambridge and the Oppo each have two HDMI outputs, and both have both digital audio coaxial AND optical outputs. Further, they also have a separate stereo output, distinct from their 7.1 multichannel outputs. The Marantz and the Denon have 7.1 analogue out, and a separate stereo output I think, but only one HDMI output and only one digital audio output, which at that price really is a bit sparse. I mean, my 3-year-old £300 Panasonic DMP BD80 has an HDMI outptut, 5.1 multichannel analogue, a separate stereo output, and both optical AND coaxial digital outputs. For me, the two HDMI outputs would be quite useful, and the two types of digital audio output.
I guess as has been said before you'll have to try to listen and view the Blu-Ray players side by side, but you might have trouble finding a dealer who stocks more than one of them! HOWEVER, one such dealer is Peter Tyson. Note however that of the two you mention, there is a notable difference in the price - PT lists the Marantz at £800, and the Denon at £650, so that perhaps says something.
When I have a spare two hours I'll list all my equipment in the parlour, kitchen and bedroom. With the exception of my two Pioneer TVs and my Denon Blu-Ray/Receiver combination, never has so little money been spread so thinly over so many boxes!