Fortunately, real-time vendors and open source collections offer plenty of off-the-shelf, ready-to-run software packages to fit most embedded computer configurations. The challenge will be to analyze your requirements to match an operating system to the application with ample room for growth while minimizing the cost and development effort. Although a commercial OS can be expensive, cost savings is an important reason to purchase an off-the-shelf product. If you can purchase and therefore eliminate the coding debug. The wide open embedded computer source products are generalized in order to fit the widest array of users and can force designers to modify the hardware configuration, resulting in higher recurring cost for the embedded device.
refer to : http://embedded-computing.com/articles/choose-right-embedded-operating-system/
