The model looks better in preview because there is a cubemap to make reflections look nice. Use either a sky light with a cubemap of your space scene or use a scene cubemap in the post processing to simulate reflections of the surroundings. Placing Sphere Reflection Captures in your scene might help if you have stationary or static lightning in your scene.
Wow. Looks like post process volume and skylight were exactly what I need for my scene. I still need to play around with values to get perfect result though. Thanks!