For the two hand bowlers. Only time will tell how long their bowling days will be. When you are young you can bend backwards and throw the ball. Let's wait when their delivery stance and finish starts to feel unpleasant. Which one will give out more quickly. The spinal or knee support. The two hand delivery looks powerful but it comes with a price. Again, only time will tell. At your teens, wow! twenties, great! thirties, fair forties, uuf!. By then you cannot stand completely straight and cannot bowl when you are in your 50's and 60's. Just give a thought into the mechanics of the movements involve and the long term effects of said movements.