Only real advantage is that you can test different tactics and the strength of your team without the consequences of losing a match. Could also be a fun challenge with your friends.
And of course the flip side of this is that your opposition can scout you better, because you have an extra game to look at, so it's as much of an advantage as it is a disadvantage
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."