there is no compare functionality as such. What I would suggest is going into the All Methods grid, press Ctrl + A, then Ctrl + C and pasting the results into Excel. You can manipulate the data in any way you want from 2 results files from there.
A similar post to yours can be found here with some discussion about the problems trying to do a comparison and what you would actually want to see.
http://www.red-gate.com/messageboard/vi ... php?t=8950
Perhaps you would like to give your thoughts on these problems and what you would like to see specifically.