I primarily rely on my Varia radar unit, but I also have a Hafny Bar-end Mirror installed. Prior to getting the Varia unit, I relied on a Hafny mirror. When I got the Varia, the Hafny was already installed, so I just left it. Since then, and 3 bikes later, I continue to use both. If I was forced to have one or the other, though, the Varia would be my easy choice. I will not ride without it.