Ubuntu

As a developer there is often a point in your career where you take a look at the number of client databases installed on your hard drive and start thinking "boy, I hope that data never falls into the wrong hands." And, if you're like most web developers and use a laptop, the chances of having a laptop lost or stolen are surprisingly high. It happens to the best of us.

Further, chances are quite good that you are using Windows or Mac for your working environment but want to run your sites in a Linux environment just like you have on your servers.