While its hard to say which of the cameras is a better still photography tool,it s quiet evident that Nikon took the lead on the HD side:
-Uncompressed HDMI output: By using the camera’s HDMI port instead of the CF or XQD card, users can stream an uncompressed full HD signal directly out of the camera
-Full-time AF - In addition to manual focus, four modes are available, including normal, wide area, face detection and subject tracking, which uses fast contrast detect AF to accurately focus while recording video and in live view.
-Multi-area Mode Full HD Video: FX/DX, and 2.7x crop mode at 1080p video modes - Whether shooting for depth of field in FX format mode, or looking for the extra 1.5X telephoto benefits of DX mode, the high resolution sensor of the D4 allows videographers to retain full 1080P HD resolution no matter what mode they choose. With the 2.7x crop, users can experience ultra-telephoto benefits in full HD resolution all at 16:9 aspect ratio
On paper this represents a real leap forward in Dslr movie making: Expanding possibility for experienced cinematographer but also helping still photographer(weddings,ceremony,journalist etc.) shooting movie on the fly without getting stacked with manual focus issues
Is Canon going to retouch the 1DX movie capability before releasing the camera?
I really hope so!!