I have a question, does higher speed films pull more contrast out of a scene?
My thinking is that if a film is more sensitive to light, then it exagerates the differences between brightnesses.
In practical reality, it just depends on the design of the stocks -- the Kodak Vision, Vision-2, and now Vision-3 line have generally been designed to match as a series, with listed exceptions. So the gamma / contrast should match between stocks in that series, more or less.
Now it's probably easier to design a high-speed stock that is lower in contrast than a super slow-speed stock like 50D because you have a fast and slow layer for each color that you can play with, tweak the sensitivity. The new higher-speed Vision-3 stocks, for example, take advantage of technology designed to make the Vision-2 50D stock possible, i.e. less grainy than the EXR 50D stock before it. Kodak figured out how to make super-small, slow-speed grains for the new 50D and then used them in the slow layer of the new Vision-3 500T in order to capture another stop of extreme overexposure detail.