They basicly do the same thing. Allow you to create a planet with a working rotational gravity. And i LOVE the idea! But these are some old mods for even older mc versions. Im not good at coding and modding so i cant remake them into new version but i hoped someone talented would see this post and think about either making his/hers own mod that allows for the same thing as these two or at very least merge them togheter/portthem to newversions! Please i cant speak for GravityCraft but StarMiner mod is to die for so im guessing the other one would be also cool to try out! And thankyou for taking the time to read that post and commenting if you did.