OGRE is a scene-oriented, flexible 3D engine written in C++ designed to make it easier and more intuitive for developers to produce games and demos utilising 3D hardware. The class library abstracts all the details of using the underlying system libraries like Direct3D and OpenGL and provides an interface based on world objects and other intuitive classes.
We consider the results of our GL3Plus RenderSystem as the gold standard. The respective shaders are generated by the RTSS component with per-pixel specular lighting. Therefore the legacy render systems naturally have differences due to the use of fixed-function. However, when rendering diffuse surface both produce pixel-perfect results:
If you want to dive deeper into the OGRE ecosystem here are your options.
There are 3 books written on OGRE
Beneath the OGRECave umbrella you can also find some useful OGRE Add-Ons like