I'm going to guess that doing it in camera is better than after the fact.
The reason for my guess is that in camera we are working with 14 bit color depth; however, after the fact, we are working with 8 bit color depth.
You can bend/adjust the light curve some with 8 bit color depth, BUT if you go too far, the different shades or steps between each shade of color may start to show. If it does, solid colored areas may show up with bands of slightly different colors.
I've been curious about this myself. Redrock advises turning off gamma settings while using the M2 because it will give you more light. If I have time I will run a test. I may not have time so if you want to try it, just setup two scene files. Say F5 with gamma and F4 without and switch while shooting. Then try to match the difference in post...
I always like to get it as right in the camera as I can. If I'm not sure, I'll use a standard setting and tweak in post. I try to get exposure dead-on, but if I leave latitude, I find it is far better to overexpose a little bit than to underexpose. Really no different than film that way.