This is a hard question. For some time, everyone seemed to favor a bare leg-summer or winter. I personally think this tend started in California–definitely not in Boston during the winter.
Go with bare legs: if it’s summer, if you have young and unblemished or veinless legs, if you have a great tan (faux or real), or if you are comfortable with the look.
Kate Middleton is wearing hose. Many fashionable women have adopted black tights. Both looks are really great! I like the edgy clean look of black tights–plus they hide a lot of flaws. I think we have reached a place where you do what works best for you.