Canon 1D 4 versus 1DX and 5D Mk3

[speedy27]

Help needed, please!

I use the Canon 1D4 for motorsport and am very happy with it insofar as auto focus performance is concerned. Far from perfect, but very good, imo. I am getting a second body and am stuck choosing between the 5D Mk 3 and the 1DX. Optically, there is nothing (that worries me) to choose between them, BUT I don't want to take a step back in terms of missed focus shots from the 1D4.

I'm therefore keen to hear from anyone who has used the 1D4 as well as either (or both!) the 1DX and 5D3 for motorsport as regards (i) how the 1DX and 5D3 compare to each other in terms of auto focus accuracy and (ii) how either or both of these bodies compare to the 1D4.

I typically shoot single frame, so the amount of shots per second is not what I'm looking to rely on in the hope of getting more in focus pics!

IF anyone reading this has directly experienced any of these camera's trackside, your thoughts would be appreciated as regards the above.

Many thanks!