Back in my rep days, half a lifetime ago, I sold Bell & Gossett circulators. We didn’t have a viable zone valve available at the time, and when the factory finally showed up with one, it ran on a wax-filled heat motor that was about as slow as I am now at 73 years old.
It seemed like Honeywell had most of the NYC/Metro market sewed up for zone valves back then. Their unit opened with a motor that pulled a ball away from a seat. They claimed that this was a great way to go because the ball rotated in the flow of water and always changed the way its rubber surface met the valve’s seat. That had a lot of appeal to the trade because it made sense. The zone valve should last longer if it’s taking advantage of the entire surface of the rubber ball.