Demoed both iron shafts
Dynamic gold had a lower launch angle but higher spin rate for me. This means an iron shot that ballooned a bit. KBS tended to have a much boring trajectory, launch angle was a few degree's higher, but the spin loft was slightly lower, and this ended up with a nice trajectory.
Also the feel is much better on KBS. The Dynamic gold is just to unresponsive for me. For me it was night and day versus the two.