I cant tell you the difference because i have always had KBS shafts and they are incredible. But if i was you id go with the KBS. 

The Project X has a shorter, thicker walled tip section which helps provide a lower ball flight and less spin.  The KBS shaft has a livelier tip  for a higher ball flight and more spin.

The best thing to do is get fitted. They will help you find the best club & shafts for your set. Don't try to figure it out yourself, go to a local golf shop and talk to a certified fitter   :-)