i bought the game and played for about 4 hours. definitely a bit different than terraria. on the plus side, i now have around 2k plant fibres.

If you like aesthetics, go for Starbound. For functionability, it's Terraria.
For Starbound, you need to explore different worlds to get what you want. You can't stay on the same planet until you have progressed far. Also, beam me up, Scotty.
For Terraria, everything is in your world with the exception of the type of contamination you get in your world (Corruption or Crimson).

I own both games. I can't say much until I've tested Starbound enough to give more info.