In a head to head battle it would be hard to tell because Ozai doesn’t have any drawbacks and can shoot lightning and Endeavor does have drawbacks although his quirk is overall stronger. In an extended battle Ozai but in a head on shorter battle it could go either way with Endeavor having more fire power but Ozai being able to shoot lightning. Although I would think Endeavor would win by brute force. But for who’s a better parent o would say Endeavor because he fells remorse for what He has done and is trying to change but Ozai feels no remorse and is the “villain” in avatar so Endeavor is the better parent.