The chines help form the cross section shape of the kayaks. Rounded multi chine shapes are slightly more efficient moving through the water but have the weight of 4 extra beams and about 30 extra lashing. Angular single chine hulls respond to leaning or edged turns a bit better and with fewer parts are lighter and faster to build. Both shapes have good initial and secondary stability. I paddle both styles and don't notice much difference in performance between them although lighter is always a nice thing.