I am looking between 1DX and 5D mark III.
So looking to see what are the differences between the two. The ones i can see are
10. ISO difference - If the native is 1 stop lower on 5D Mark III, that means most probably the usable ISO is ISO 1600 and can go to ISO 3200/6400 in tough situations. For me coming from 5D, this is atleast 2 stop increase already for Mark III. And for the dance concerts i do take it is sufficient. There is enough lighting on the stage for me to be happy with a 2 stop increase. So professionally i am good. Personally higher ISO will allow me to take photos of parties etc without the flash and capture more of the ambience. So 1DX has an advantage - tiny bit only.
Anything else that is different. Anything else i need to consider?
The 5D3 will not be 2 stops better than 5D in high ISO performance.
Perhaps 1 stop. Perhaps even 1.5 stop as would be extremely good and better than D3s. Certainly not 2 stop.
Well, if the 5D3 will be one stop better over 5D2 (or as you put "5D" do you mean the 5Dc?) then ISO 12800 will be equal to ISO 6400 which I guess would yield nice b/w photographs. Compared to my current 30D which I shoot as up to ISO 3200 (H) well exposed to the right.
I won't be in the first wave of buyers, but one year from tomorrow seems great. This will be a lot of camera for an amateur like me, let's say for the next five to six years for sure. I am completing my fifth year with the 30D this April. The new 5D is the dream camera for me and I can't wait to test it with a fast lens 50/1.4 at ISO 51k in real low light with only a slightly iluminated face for the AF trying to lock on

rock'n'roll, gentlemen. enjoy the new day coming!