Majin Buu can tear a hole in space and use it for inter-dimensional travel. Can Lord Beerus do it? Also, Majin Buu has regenerative abilities. What would be the outcome if they fought?
If Beerus uses his divine power he can erase anything inside his universe can he not?
That means that even if Buu were stronger Beerus can erase him if he wishes to do so.
This is because as the God of Destruction, he has to destroy other planets so new planets may arise and give new life. The overwhelming power of Beerus exceeds even that of Goku, who has surpassed several Super Saiyan levels; Beerus completely dominates Super Saiyan 3 Goku in battle, of course beating Goku in Super Saiyan 3 by just two hits by flicking him and rendering him unconscious with merely a chop to the neck. He also takes down Mystic Gohan with a single kick to the abdomen, causes Gotenks to defuse, and dominates full-powered Super Saiyan 2 Vegeta as well. Even when Goku fought him after becoming a God, he merely impressed Beerus rather than inflicting any long-lasting damage.
Beerus is stronger and can erase Buu. Regeneration will not work if Buu does not exist.