If I'm being completely honest, I just thought Jotaro would win because he's the main character. I mean, a 17-year-old student from Japan couldn't possibly beat a 120-year-old jacked-ass charming vampire with a physique superior to Arnold Schwarzenegger. But Star Platinum has better stand stats than even The World.
The World has an A in power, speed, and durability, B in precision and growth potential, and a C in range.
Star Platinum has an A in everything except range, where it has a C, just like The World's)
I'm guessing Star Platinum's superior skill in precision (SP: A; TW: B) is to thank for this. Using its precision, it can generate more powerful punches than DIO's. And Jotaro was really angry.