Based on what I know (I own a Kaimana,) the Kainalu is a modified Kaimana essentially with a lower deck and seat, the seat/cockpit is 6" more forward than the Kaimana and the hull has not changed much from the original Kaimana hull. It's a tiny bit narrower from what I hear but not much. The Ama is the same between the two Kaku boats. I have paddled a Hurricane and given it's lower volume & narrower profile, in the flats I'd say the Hurricane is faster. By how much I don't know yet. It's the motor that makes the biggest difference.
Overall if I wanted a boat that was good in the flats and surfed well, I would take the Kainalu over the Hurricane but again that depends on where you live and what your water conditions are like. Here in the North-East (mainland) the Hurricane works well in small to medium stuff which is mostly what we see, but from medium and up I like my Kaimana better as it is a much better bump and surf boat. The Kainalu is essentially an "improved" Kaimana and a very good versatile boat in multiple conditions. Can't go wrong with that ride.