I prefer working in color, personally! I like doing lighting studies and such in grayscale, but I vastly enjoy everything about coloring from the flatting to the effects rendering. And the colors themselves. I have made a gray scale comic before and it was also enjoyable, but I think most of the time I would choose color.
For reading I don't have a strong preference. So long as the art is clear and easy to read, I enjoy both color and b&w comics a lot! And there are things in each type that can add to and take away from clarity, so that doesn't really matter.