Starbound has much better worldbuilding than Terraria. The races all have interesting motivations, backstories, rivalries, settlements, artifacts, themes. Terraria is better in many aspects, but the themes of the game are pretty generic.

I’ve finished Starbound twice. Tried Terraria because the popular opinion, as you say, was always that it was better than Starbound, but honestly can’t get more than a few hours into Terraria before getting bored.