I have used flapper style, Y style and ball style. All present friction head to the pump, so need to factor that into your pump choice. I found the flappers to be the worst of the three with a high propensity to stick, the Y style in the middle with the weighted plunger tending to get stuck up the passive arm (easiest to clean, though), and the ball style to work the best. Trouble is, none of them reliably seal completely so are essentially useless as a longer term backflow solution (i.e. protracted power outages).