I'm shooting a Canon 1DX - I'll ask my pal at Canon what he thinks. Even though the Digic 4 is 14 bit, I think the sensor still collects data in the same fashion, so although the numbers of available tones would change, the percentage collected for each stop would remain the same.
In the meanwhile here are some before and afters, histograms included.
20090612_Bahamas_UW_1343_ETTRc.jpg 197.75KB 29 downloads
20131208_Komodo_00640_ETTRc.jpg 251.01KB 28 downloads
20150428_Bonaire_0656_ETTRc.jpg 296.61KB 27 downloads
20150430_Bonaire_0872_ETTRc.jpg 227.8KB 29 downloads