Anzogh and Onatel, for offense who should get
In my honest opinion, it depends on who else you got in your line up.
I have both heroes, neither in my defence teams, but I gave my spare emblems to Onatel
Whichever hero you choose, good luck
@JGE is right. The forum users would be able to exact an intelligent suggestion if we know your other maxed heroes. AFAIK, Anzogh would be great offensively, especially when paired with Wilbur, Falcon and attack buffer like BT or Zim. However, Onatel is a gem, sturdy and a bit hard to crack, ideal at flanks.
If none of both are on your def, you may spread the talent nodes to get 2 decent attackers.