Reflective displays have the advantage of perfectly adapting their brightness to their surroundings. This is especially useful for portable devices. Emissive displays can have light-sensor-controlled brightness, but they don't adapt pixel by pixel like reflective displays.

However, if you are using an emissive display in an environment with constant and even lighting, you can set the brightness correctly and it will be just as good. Many people in such lightning conditions configure their displays wrong and mistake the misconfiguration for an inherent disadvantage of emissive displays.