Quote Originally Posted by neuroanatomist View Post
Chuck Westfall has stated, "...the EOS-1D X achieves a higher lens motor drive speed with select L-series USM telephoto lenses than the 5D Mark III because of the 1D X’s more powerful battery pack."
Of the lenses Chuck Westfall is referring to, the 85mm would be on the low end of the amount of glass that has to be moved to focus. Not to mention the amount of power to drive one of the large telephoto's IS.

I hear few complaints about the 7D used for sports mated to a 300mm f/2.8L IS, 500mm or even 600mm. I doubt the 85mm would eat more power than these lenses.

Possibly if we knew someone who had a 7D, 1D X and a 85mm F/1.2 he could do a few comparisons. I wonder who we know around here has all of these