As already stated, you have the same options here as in the A drop-down menu. How you find out what lists are relevant to compare, we will leave entirely up to you. While some lists (or songs) will seem more logical to compare to each other, we are sure that you can find hidden gems in seemingly illogical pairings. 

Choose a second list of songs for the B tab in the comparison tool.

Enable COMPARE in the comparison tool to see both your selected lists in the analyzer meters. This lets you compare the chosen A and B lists to each other.

Alternatively, by selecting a specific track in the A list, you can compare that particular track against the full B list. By also selecting a specific track in the B list, you can compare two specific tracks against each other.