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As far as I read, transferring 14 raw images to the cards will require too much bandwidth than the 1DX has to the card, while 14 jpg files are much much smaller. The dual processors are very fast, but its not about them.
If each file in raw is about 27MB, 14 FPS will require 378MB/s in perfect conditions.
Even when the camera write-ahead, it will still chock at some point when it won't empty the buffer fast enough. With 12 fps, you get 38 images. I guess with 14 you will get much less.
Even the 1000x CF cards will only give you 150MB/s, which will not be enough for the 1DX to give you 14 FPS and won't fill the buffer too much.
Once the buffer is full, you might end up with 2-2.5 seconds waiting with the buffer being cleared, which is 2-2.5 seconds you are missing shooting the action.