Fat B***rd, I rate Jeffries higher as Jeffries fought Corbett twice, and knocked him out both times, though it was late in Corbett's career. In his prime Jeffries was a great puncher, had a granite chin, and was surprisingly very fast on his feet (slowed down and past his prime when he fought Jack Johnson). He just seemed to have been on a higher plane than Corbett and many others of his era and the immediate preceding era.
One thing to remember is that John L. Sullivan, Jeffries, and many other white boxers drew the color line (Burns to his credit finally agreed to fight Johnson)and refused to fight black boxers. Greats such as Peter Jackson, Sam McVey, Joe Jeanette, and Sam Langford never had a chance at the title, so the record books are filled with black fighters boxing each other multiple times. Jack Johnson, when he became champion, also drew the color line against other black boxers, not wanting to risk his title against the likes of Langford, Jeanette, and McVey.
There's a bittersweet, poignant film clip of Jack Johnson and Joe Jeanette boxing each other in an exhibition fundraiser when they were old men. They're smiling and enjoying their friendship as they move about, clinch, and throw soft punches.