The advantage of the McMahon system over the Swiss system is that it requires fewer rounds to find a winner, and that it avoids extreme match-ups (very strong players against very weak players) in the earlier rounds. By matching up possible tournament winners earlier, the system allows for more games amongst this group, and thus improves sampling.
The McMahon system has several benefits over the Swiss system, including requiring fewer rounds to find a winner and avoiding mismatched games between strong and weak players in early rounds. This allows for more games among top contenders, ultimately leading to better representation through sampling.