When i teach, i always play the defender. I think the defender is harder to play and given it 'mathy' aspect i think new players would have more fun playing as the attacker (i taught this game to 4 different players and they all really enjoyed playing as the attacker.) I prefer playing with the attacker, but i always teach as the defender.
Also there are a lot less actions the new attacking player needs to know before he can start playing.
As the defender there are so many actions and many of them are situational.
The big drawback of this is that I am almost always the defender