I want to do a real quickie user study for my thesis, and would like your help. All you have to do is look at the curves below and choose your favorite. Then, in the thread below, tell me which one it is. It would be best if you don't look at the responses first.
What are you looking for? Above all, smoothness (or "fairness" in the CAD lingo). Anything that looks like an unsmooth transition should be rejected. All these curves are fairly smooth, so you're just choosing the best. Another way to think about it is, if you put down points at the peaks and valleys and asked the computer to draw a smooth curve through them, which one would you prefer?
Later I plan to do this as a more controlled user study, with an interactive slider. But I want to get a rough idea of the range of curves that people find most attractive.