The table below shows some key percentages. For the percentages, I divided by PAs (with IBBs and SHs being taken out). I included HBP in walks.
Strasburg has the big edge in SO% while Sale is ahead in HR% and BB%. Now let's say they each face 36 batters in a 9 inning game and we use the values from the fielding independent ERA. At 1.4 runs for a HR, Sale is just about .2 runs better. On walks, at .33 runs for a walk, he is also about .2 runs better. But using about .2 runs for strikeouts, Strasburg is about .41 better. That makes him about .1 better.