Obviously the 1D is your better body, for wide angle work.
Some facts & opinions about Canon lenses wider than 24mm:
– there are precious few brilliant options
– there are no options faster than f/2.8
– both the 16-35/2.8 and 17-40/4 are popular and not to shabby once stopped down to f/5.6 or 8.
– when used wide open, neither will deliver corner to corner sharpness, although it can be argued the subject is in the central part of the frame so border sharpness is no issue.
– If IQ at wide aperture is paramount, then you’d need to look at 14/2.8 or 15/2.8FE or 24/1.4..