I stick with 8gb cards so that if it goes bad or gets lost I have not lost everything
I would rather have 8x4 than 1x32
Believe me cards do go bad and I could loose an entire wedding over one bad card

In the 5DIII I also use a 16gb SD card and use it as a backup for the CF cards.
This dual card function was one of the selling points of the 5DIII
Guess I grew up on CF and still use them as primary.