Hey, I don't fly 'em I just run 'em..My only basis for comparison is what they do with the same prop...I once tested 4 NIB G62 engines for a pylon racer..The best was 400 rpm better than the worst..It's impossible to make engines exactly the same, so some will be faster than others..Ford fanatics won't buy Chevys, same thing....We're fortunate we can have competition, it makes for the best engines....