I keep my setup very simple. I shoot everything with either a 400 f/2.8L or 300 f/2.8L on my main camera, and then the 70-200L II IS on the other camera. It's a pair of 1DX's, so FF, and this setup works well for me.
I do notice the 400 f/2.8L I IS AF's much slower than the 300. I have a higher miss rate with the 400, even on a 1DX.
Lucky git with two 1DXs! But yes, would prefer a 400 mm and a 70-200 on two 1D bodies.