Story, systems (maps), ships. Base game gets improved along. Recycling is new feature (those compacted cubes flying around I guess) - sounds like flagship feature with the DLC but available in vanilla too - probably a bit simplified. Find big conflict zone and you can build a new base for your economy with the scrappings. DLC system has natural phenomenon that is destructive and intended to tie into the recycling feature. Even better energy output than Mercury sector. Indeed piracy is one of the foci of the DLC. Updated vanilla capital ships (new variants).