I used two groups, smiles and no smiles. It just happened that way when I was creating my groups: I made sure I had a least one of each job in each team. That meant Fang isn't in the same group as either Snow (sentinel) or Vanille (saboteur).
I ended up using mostly Lightning, Fang and Hope. Why? They have more attack power than their equivalent in the other team(but less HP), making for faster battles.