With the samples on The Digital Picturekennykodak said:i am totally happy with my Canon 14L II. no complaints.
Canon 14L II vs Nikon 14-24:
Distortion - Nikon distorts heavily - the canon wins by a big margin here
CA - Similar (slight edge to Canon)
Corner sharpness - Canon wins
I would buy the Canon at the more expesive price point for 14mm
The Ziess seams on par with the 14II in most reaspects. The 17tse kicks ass in all aspects. Ziess can hold filters - a big plus for landscape work.
Why do so many people glorify the Nikon 14-24 over Canon and Zeiss offerings. Price maybe, but thats all