Between the black and grey. I think the black looks best from a distance but it also has a stark contrast, where the grey feels more balanced to me,up close. Also the grey is not just grey but more of a light taupe that I quite like. However the black seems to absorb the red from the pr better. In the grey dial, the red pops too much for my taste.
About size. There is no doubt in my mind that the 40 is the best size, even though I have a larger than average wrist.