Just checking out Arroyo's page on Baseball-Reference. I just happened to notice that his #1 "Similar Pitchers" is, you guessed it, Aaron Harang. Of course, Harang's #1 comp is Arroyo as well. Other notables include Jake Westbrook at #3 for Arroyo, #8 for Harang, and Tomo Ohka at #10 for Arroyo.