The Denon will have far superior room correction (Audyssey MultEQ XT32) VS. Sony's DCAC calibration which will have a big impact in the sound of your system. The Denon has pre-outs so you can add an external amplifier down the line for more power.
I'm also sure the Denon will get closer to the acutal rated power specs - a quick look at the back of both receivers reveals a power draw of 675 watts on the X4000 and just 240 watts on the Sony.
There's a ton of information on the new Denons in the official thrrad here. Take a look for a complete rundown. IMO they are not directly comparable. If you're looking at Sony you should be looking at an ES series AVR to compare.
ht Panasonic TC-P60ZT60, Monitor Audio: Silver RX6, RX Centre, Radius 90HD; Martinlogan Dynamo 700, Marantz SR5006, PS3, Oppo BDP-103D
2ch Marantz PM8004, Sony BDP-S1000ES, JVC T-X3 tuner, Monitor Audio Silver RX1, REL T3, Apple TV, Peachtree Audio DAC•iT
lr Panasonic 50ST60, Sony BDP-S5100