I picked Klitschko. From what I've seen Arreola likes to brawl and throw wild shots which will easily be avoided by much taller Klitschko. Vitali by TKO.
As I said on the other poll, Vitali TKO7. Arreola throws some hopeful hayemakers, trudges forward into heavy jabs and right crosses, gets ground down for an accumulation stoppage around the 7th.
Vitali by knockout or TKO. Could be mid-rounds, or even a little later. Vitali takes his time to see his opponents up, however, if Arreola goes after Vitali early, it could very well be an early knockout.