Comparing lenses across bodies, not to mention brands is a big no no. Since the 14-24 has been tested on Canon bodies many times, its theoretical performance is well known.
Unfortunately, some of us (ME) are really poor at manual focusing, and I'll do better with even a inaccurate aurofocus when trying to focus manually using a viewfinder. I do a fairly good job using the LCD at 5 or 10X assuming I can see it, which is also a issue in sunny weather.
I bought a D800 intending to get a 14-24, I bought a 24-70 2.8G, a older 80-200 f/2.8, and a 200-400 AIS. The CA was horrible on the 24-70, the 80-200 was a fine lens, and the 200-400 had so much stiffness in the focus ring that it was unusable. After such poor luck with $5 or 6K worth of lenses, I dumped everything before getting to test the 14-24. Its not my first bought with quality issues and high end Nikon lenses, I had a 300mm f/2.8 that cost me $800 to get it working right. I do have a 200-400 f/4 G VR1 and its a supurb lens. I haven't used it on my Canon bodies due to lack of aperture control and my inability to manually focus. The lens is excellent at f/4, so I might give it a try using liveview.
The only issue I've had with maybe 100 or more Canon EF lenses was a used 50mm f/1.4 that I bought used and discovered it was damaged. That cost me the flat rate $90 repair, and then it was fine.