The Hydraforce valve looks like a much better valve than the Pollak valve. There are accounts of the Pollak valve malfunctioning, where the motor drive sticks while switching ports. I have not experienced this issue personally but maybe it's just waiting to happen. I believe the Pollak valves retail about for about the same price as Hydraforce valve. It's best to shop around. I have found new Pollak valves for under $30 shipped on ebay.