Choosing an RTOS is not as simple as choosing a car. We know about cars; we know their strengths and weaknesses and we intuitively understand compromises like performance vs practicality or luxury vs price. We see all kinds of vehicles on the road, so the range of available cars is obvious. When choosing an RTOS, the middle ground is crowded—dozens of general-purpose RTOSes with broadly similar characteristics compete. They all have a scheduler, services, libraries, middleware, technical support, and graphical tools. Any one of them could genuinely do a good job and so choosing between them is a mixture of quantitative metrics (like features and price) and qualitative measures (like past-experience, personal-preference, and reputation).