There are also a lot more ships and weapons to play with, as well as Marines & boarding pods for capturing capital ships and missile corvette-class ships (M7M), but I can't say much about those as I've barely scratched the surface of the Terran plot, let alone anything else! You can also assign groups of ships to 'wings' to make group/fleet management easier. And the encyclopaedia is a godsend - means you don't have to spend hours searching for a particular weapon or upgrade is sold, and provides lots of helpful information. The dialogue isn't miles ahead but the character visuals are a little better, as are the visuals in general. The interface is better, the amount of missions/plots/things to do have increased dramatically and been made more obvious with icons on ships & stations.
Playing R gave me a good understanding of the basics and has made my start in TC much easier. I'm not ashamed to say I scripted & cheated loads in R simply as a survival mechanism so I could keep playing the game in the early stages, it was so complicated (in terms of weapons, ships, stations etc)! I had similar feelings to you playing R - story was ok, but not enough of it - and the complexity was overwhelming. I've just made the jump to TC after playing Reunion while I waited for my new PC to arrive. Might be 'Gold Edition' because it contains both Reunion & Terran Conflict, same as I got recently.