Both are great drummers, but Copeland played a lot of synchpated beats, which are difficult. Peary was an innovator as well, especially with his double bass set and speed pedals. Overall, Copeland is much more accomplished musician -- check all the scores he's worked on.
Buy that man a cigar!
Remember, sometimes less is more.
Does the answer change when the two only have a 3 or 4 piece kit. Think of Seve in the bunker with a 3-iron.