After I acquired my 1DX in July, I wanted to ensure that I had the fastest CF cards for continuous shooting. I had always used SanDisk Extreme Pro cards but was concerned that their cards were rated at 82% of the comparable Lexar 32GB cards in the Galbraith review. I have never lost an image on a SanDisk so I was confident in their storage quality but the speed bothered me. I even contacted SanDisk to see if they were releasing faster cards soon and I got a "dance around" answer that did not indicate they were. Today, they still do not offer faster cards. Therefore, I purchased a pair of Lexar 1000X 32GB cards that were on sale at Adorama for $234.95. There was a big run on that deal so it required 3 weeks for them to arrive.
I have used the Lexar cards exclusively since they arrived and always shoot with recording to both cards. I have yet to hear the 1DX stop recording in a burst mode of 12fps whereas that occurred frequently with my 10fps Mark IV with the SanDisk cards. I am pretty certain the Lexar would stop recording if my burst was long enough but that did not happen in the two football games I shot this fall.
I highly recommend Lexar and unless SanDisk matches their speed I will not purchase SanDisk again.