Export materials is how you want your material file to be created. It is best to at least change "scene" to match your mesh. otherwise, every-time you export, the scene.mat file will keep overwriting itself and mess up older meshes.
Rendering materials is the option you want if the mesh has 1 texture. But you'll have to punch in the right code after the file is created. (I usually snag one from FH lol)
Game Engine Materials works best for multiple textures but will give you a pretty long mat name for each texture. (ex: tex/aplha/imagefile.png)
