Ball valves are known for their reliable shut-off capabilities and ease of operation. They use a spherical disc to control fluid flow and are ideal for on/off applications, such as isolating sections of a system for maintenance. Butterfly valves, on the other hand, utilize a rotating disc to regulate flow. They are lightweight, cost-effective, and suitable for large pipe diameters. Butterfly valves are commonly used in cooling towers and air handling units where quick shut-off is needed.