Axiom is supposedly alright, not amazing. Its a full port of Ogre3d to C# (yes that is right, it isn't a binding it is a full source code porting). Its slower than MOgre (which is a binding to Ogre3d) but is also porting an older version (MOgre is only 1 release behind ogre3d, axiom is an ancient release of ogre). From what I here it doesn't work on mono too well either (which is the only disadvantage on paper for MOgre). Its generally not the best library unless there is a specific reason for not using Ogre. Ogre3d (the original C++ graphics engine) although is nowhere near as complex as raw openGL or directX (with C# that would be through tao or slimdx or sharpdx) still isn't terribly easy to use, it also doesn't provide anything other than graphics, its not a full game engine. Ogre I think is meant to be object orientated graphics rendering engine, so no sound or physics or anything. MOgre/Axiom would be a pretty good choice for a AAA quality game in C# but not for a newbie. Of the 2 MOgre is almost universally better than Axiom.
: : Removed response to off-topic post which was split into a new discussion.