Water Pump Vanes (propellers)

A few years back I had to change water pumps. The 8 vane pump was replaced with a 6 vane one. Non a/c car.
I compared the two and the vanes on the 6 vane pump were larger. The 8 vanes were longer but not as thick. I never measured the vanes on both of them to compare the total vane surface area.