I would take Klitchko in MMA or Boxing. Either brother, both are tall, good boxing skills, strong jabs an 10x the knock out power tim has, not to mention much more speed.
Oh an they were kickboxers too, Vitali was a pro kickboxer an wasn't that bad, so i would pick against Tim in either sport.
I would take Kelly Pavlick against Tim. That weak ass slow jab isn't going to cut it in boxing.