Super Buu is a combination of several powerful beings, including the evil wizard Babidi, the powerful Majin Buu, and the Grand Supreme Kai. Super Buu is incredibly strong and has a variety of powerful abilities, such as the ability to absorb other beings and to regenerate himself.
However, Kid Buu is the original Majin Buu, and he is said to be the strongest of all the Buus. Kid Buu is incredibly powerful and destructive, and he is not afraid to use his power to destroy anything in his path. Kid Buu is also incredibly resilient, and he is able to regenerate himself even after being severely damaged.
In a fight between Kid Buu and Super Buu, Kid Buu would likely be the winner. Kid Buu is simply more powerful and destructive than Super Buu, and he is not afraid to use his power to its full extent.