shape matching: how to best address this problem

Hi everybody, I have this problem. In the figure, I need to see which set 1 or set 2 best matches my main set. Of course, you can see that pixel by pixel matching will not work as area of matched vs. non matched pixels is equal for data set 1 and data set 2. However, it is obvious, that set 2 is the better match of the two. In real application, I will have many many sets and I need to find the best solution. Each data (main and set) is represented by binary matricies. I am thinking that you can do rotation. However, I am not certain that it will work. Any suggestions? Thanks And pic is here: http://i47.tinypic.com/2mwi5na.jpg