I replaced my 5D MK III with a 1D MK IV and re-purchased a 5D MK II.
It all comes down to which features you value.
If you like AF at f/8, a focus point that lights up, etc the 1D MK IV might work better for you.
Thanks for responding. Were there any reasons that you really didn't like the 5DIII other then the two you mentioned?
I don't need f/8 focus as I generally use fast primes and don't like the results of a 2x converter.
Any other reasons you made the big decision you did? Thx...
If you are shooting wildlife, the 1.3 crop and the f/8 allows you to put a TC on. A 400mm f/5.6 lens plus a 1.4 TC gives you a 728mm equivalent. This is much less expensive than a 800mm lens, and for me, much easier to use.
I also do low light theater photography, and the inability to see the AF point in low light makes the camera almost useless in that situation. The 1D MK IV is not a good in low light, but you can see to focus, which actually translates into more keepers. I'll likely use my 5D MK II in low light, its center point AF in low light is supurb and fast.