"Super Saiyan Vegito wins this for the following reasons: Vegito has the physical strength advantage. Super Saiyan 4 Goku dominated Baby Vegeta who dominated Super Saiyan 3 Goku, Super Buu absorbed Gohan, Gotenks and Piccolo also dominated Super Saiyan 3 Goku along with Vegeta so this version of Buu is likely to be as strong if not slightly weaker or slightly stronger than Baby Vegeta. Vegito in his base form was more than a match for this version of Super Buu in terms of physical power and when he transformed into a Super Saiyan he completely dominated the fight. Vegito also takes this in terms of speed. Super Vegito had intense speed to the point of overwhelming a being as fast as Super Buu absorbed Gohan, Gotenks and Piccolo who overwhelmed Gohan with his speed and it should be noted that Gohan is functionally one of the fastest DBZ characters. Super Saiyan 4 Goku hasn't shown much in the speed department. It is highly likely that Vegito can transform into a Super Saiyan 2 and Super Saiyan 3. Goten and Trunks after having watched Goku transform into a Super Saiyan 3 learned how to transform themselves as Gotenks possibly because they had the sufficient amount of power and mental capability to transform into a SSJ3 and they briefly displayed the SSJ2 form during their transformation to a SSJ3 as they required to bypass SSJ2 in order to achieve the SSJ3 form and since Goku and Vegeta have already full control over their Super Saiyan forms and even more Goku knows how to transform into a Super Saiyan 3 it is highly likely that Vegito can transform into a Super Saiyan 3 and 2 but didn't because it was completely unecessary during his existence as he was already overpowering Super Buu and had complete control over their battle. Vegito wins. "
I have to disagree with you, because baby mopped the floor with Majuub, and also, unlike Baby, super buu gohan was not unphased by ssj3, super buu mopped the floor with goku and vegeta, but was still getting hit a few times. Baby was miles ahead of Gt ssj3, I would like to point out that goku's base form was stronger than perfect cell easily, and so it is not that simple. Vegitto would in my opinion beat goku ssj4 if he turned ssj2 or ssj3, which he was well capable of, because goku had obtained those forms.