>> Is there something important included in .lxo files that is not included inside of .lwo files?

.Lxo stores the complete scene, that includes rendering and surface settings (modo shading tree), lights, cameras, animations, etc ...

... I don't see anything else that MoI could export that is not available with the .lwo format (surface name and colors, basic shading (color, diffuse, specular, gloss, transparency, bump), layers, multiple uv's, vertex map, morph map, and recently normal vertex map)