How can I determine best performing groups in a series
Not sure to understand what you are asking. Your purpose is to find the only one best group ?
From the picture you provided, two things are unclear to me:


A and B areas don't have the same width, how are you defining your width ? 
A and B are covering areas where the signal looks exactly the same. Is it that for the sake of the example you copy-pasted some fake data or does it have to do with what you are finally trying to do ?


If your width is fixed then you should be able to compute a series of local averages and pick out the best one.