Probably the Spinlock. It is MUCH more comfortable to use on keel boats.
The stick is designed to be used OVERHAND. Kinda like doing a curl, with your pinkie closest to the tiller. Sorta natural for dinghys with the main in your other hand, but not so much for bigger keelboats.
The push-pull motion of the grip is natural for driving a keelboat. Doing this with the stick is hard on the wrist.