Upload & Sell: Off
I've owned lots of these bodies including the 1Ds2 ( I loved that camera!) and used / processed lots of shots from the 1Ds3. I've only played briefly with the 5D3 at a show and have zero 'real' experience with it.
The 1Ds2 was a great camera for it's time but I'd hesitate to use it at ISO1600 and above if you are going to be super critical of the shadow noise. The banding was not as bad as the 5D2 but it was certainly there for all to see once you had to push things beyond a stop or so. The 1Ds3 was better but still not free and clear of the banding issues.
I always found AF to be "satisfactory" on the 1D, 1D2, 1Ds2 and 1Ds3. I've been unhappy with the focusing on the 1D3 (sold quickly) and 5D2 (kept but now only use for video).
The AF outer points are still not as good as the centre / cross points but definitely beat the lower end models (10D-60D, 5D, 5D2 etc). Low light focusing is not their forté, but once you add focus assist they can pretty much focus on anything rational even in the dark.
The 5D3 I can't really comment on.
None of them could recover shadows or highlights like Nikon 14 bit raw files which lacks the Canon blotchyness of chroma noise and banding.
Where Canon shines is the easy of processing if you get the shot dead nuts on 'in-camera'. Auto white balance on Canon is (IMHO) still way ahead of Nikon (the D800 has improved greatly) although it's usually a few shades colder (blue).