Here are the questions; Who is a better character and who'd win in a fight?
Suikakuju for me is far better seeing as his personality is shown to be quite complex (mocking, arrogant prince in the face of Amano, serious, duty bound warrior when trying to assassinate Nagumo)as opposed to Myuni who seemed to be in a perpetual state of infantile laughter and pompous gloating. Suikakuju also adds insight into the more 'noble' side of the Makai, sacrificing his own life to save his world and people unlike Myuni Hausen whos ambitions were purely self serving.
In a fight, it's difficult to say. Sui was shown to possess almost the same powers as Amano which are too many to list. The only power I've seen Myuni use was Makai mind control and using his magic rock to grant his cloak reflective abilities as shown by him batting Amano away with it as if he were nothing.
Captain, although your abilities intrigue me, you are quite honestly inferior- Khan Singh
To put it simply, Munni Hausen would win because he carries an enchanted orb that allows him to control other demons. Without the orb, however, Suikakujyu would soundly trounce him, just like Kohoki would've had Hausen not used the orb to kill him. Suikakujyu and Kohoki are both Majin from Makai but Munni Hausen the 2nd, despite his supernatural enhancements, cybernetic implants and bionic body parts, as well as his mastery of the black mystic arts and his scientific genius, is only still essentially, a Ninjin from Nijinkai. Extraordinary by human standards, but a mere mundane by demon standards. Without the orb, he couldn't even beat Jyako, Megumi or Buju. The only person he could possibly be equal to was Caesar but Caesar was not even as strong as him even though the two are very similar. So there you have it.
As previously said, Myunihausen's power comes from controlling others, namely the Makai. Therefore, without his means of control, he's as vulnerable as any other human, in theory. However, in Udoji IV, he did resurrect himself by taking some of Yoen's demon lifeforce, and I think become some kind of hybrid. He even returned without a scratch after being blown apart by a tank.
Suikakajyu was pretty powerful and pertinacious in his efforts to kill/stop the Chojin. Therefore I back him to win if Myunihausen was minus his demon orb.
Even if he did regenerate himself, he was nowhere near the level of power that he had in the 1990s, before he was ripped up by the helicopter blades. Munni Hausen used black magic to supernaturally enhance himself over the decades from a short skinny German guy to a tall, muscular half-demon guy. When he was in Urotsukidoji III, he was weakened because of his bionics. When he was in part 4, he used whatever sorcery he could to regenerate his old body. But as you can tell, he was back to being his old scrawny self. His emaciated form was the tell tale sign that although Hausen was a formidable sorcerer, his days of being a serious threat were long behind him. Which is why he needed Yoenke a.k.a. Yoenhime to help him in his schemes. The old Munni Hausen wouldn't need a demon princess from Makai for anything.