Fearless Boo said:
South Kaioshin doesn't have a gentle pure heart while Dai Kaioshin has.
Excuse. We didn't see their personalities.
What we do know though is Gotenks pre-RoSat is higher than Goku, and even if for some reason you don't want to believe Regular Gotenks surpassed that his Super-Saiyan definitely did and then add another 2 transformations on-top of that and only then is he able to fight Super-Boo for real. How does South Kaio-Shin add so much power to Kid-Boo to have him go from ~< Super-Saiyan 3 Goku to surpassing Super-Boo? Unless you think he's haxed, which there's no proof of either. Majin-Boo isn't that much lower than Super-Saiyan 3 Goku either.