So why is it if one jungler is bad and the other is good the team with the good jungler will win?
This role has way too much of an impact on the game, for the worse or better. For instance, their jungler having presence in all 3 lanes while outfarming your jungler and your jungler shows up to a lane and dies. This just ruins the game because of one role. On top of that if your jungler is clueless you won't really know if their jungler is in your lane so your aggression and ability to outplay the enemy laner is curbed.