Hey guys, The specifics on this intrigued me so I talked to a few of the true experts on this around the office and came up with the following:
Color - the first thing the synther does is convert to grayscale, so color has no effect at all. This is why you can synth scenes in radically different lighting conditions and have everything match
Brigtness - increasing this doesnt really improve the point cloud, but may make the points more visible because, well, they're brighter
Contrast/Curves - may have a small effect if it makes features stand out more, but it probably wont be a noticable difference
Given all this I would suggest you post process your images to make them look great, and not worry how it will effect the synther.