Only real difference I can think is one small use case. If someone is expressing that they're sure about something, they'd pretty much always say they were "sure OF it". Ex 1 "He'll be on time, I'm sure of it." Ex 2 A: "Will he be on time?" B: "I'm sure of it."

There is almost no difference. The only small difference might be that you would be more likely to use "sure of" when talking about something very specific, whereas "sure about" is more likely to be something a bit more general. For example: A: I saw his do it at 8:16pm. B: Are you sure of that? A: Everybody loves the music of the 1970's. B: Are you sure about that? But even in those examples, you could swap the answers and nobody would think you were wrong. Any difference is so tiny and so subtle that it is not worth worrying about.