Though I am partial to the Dart since it is a very well made boat and has same designer as the Tornado, I have heard they tend to be undersailed, meaning they really like lots of wind to go best. If your location normally gets 10+ kts of wind, the Dart should be fine. It is also the lightest boat on your list of choices. You could always add a spinny or Hooter yourself.
Mike.
I would NOT suggest the Dart unless you sail somewhere where it is 15+ most of the time. It really is under sailed. Not the gretatest design and would not take kite well. The Nacra is by far the best bet.
Sail area
Well Built
Ability to take a kite
Plates
Don't even think about the Hobie 17 if you want to take more than 1.