You don't get it obviously, nothing changes except things get more fair for everyone if they use the clan match mastermode.
Edit: Nothing of significance that will hurt the game will change anyways. Having both teams play both sides of the map for an equal amount of time will make it so 1 clan cannot pick a 'biased' map so they can have an easy win. You might be on the team with the advantage for the first half of the match, but you will be playing on the other side for the second half, so it evens out.
Edit: Nothing of significance that will hurt the game will change anyways. Having both teams play both sides of the map for an equal amount of time will make it so 1 clan cannot pick a 'biased' map so they can have an easy win. You might be on the team with the advantage for the first half of the match, but you will be playing on the other side for the second half, so it evens out.