Sprintech. Excellent value. I have 'em on two of my three road bikes, and plan to add one to the third.

The ball joint holds securely but is easy to adjust on the fly. Occasionally I knock it out of adjustment against a wall or with my knee, but it's easy to reset. It doesn't lose adjustment on rough roads.

The Italian road bike mirror is a bit more pricey but reportedly very good - a couple of friends use them. They said there's no way to adjust the mirror after it's set, so it's essential to set it correctly for your riding position.