The Vanquish Surfski has some extra volume on the back in the shape of chimes, and that support makes it super stable and incredibly easy to steer (just with soft touches in the direction pedals) giving it very precise control in every single wave. At the same time, the lift created by the extra volume keeps the wet surface similar to the 560.
The Vanquish is made for all those paddlers looking for extra speed and competitiveness but are not ready for the pure racer 560.