Who to choose... (FOR EXPERIENCED PLAYERS)

I've started a party of good characters and I'm stuck on one point - should I choose Imoen dual classed to thief/mage (If so, at what level should I dual class her?) or Coran (fighter/thief)?

The other members will be me a fighter, Ajantis, Keslick, Kivan and Neera

Any help would be greatly appreciated thanks