Interesting.
Harlow has little in common with Monroe apart from hair color and sex appeal. Marilyn onscreen was soft, with a sweetness of presence even at her most brassy. Harlow was diamond hard.
Monroe was part of the apostolic succession of 20th Century Fox blondes, from Alice Faye to Betty Grable to Monroe, who filled the mold and then broke it. They were all basically nice girls. With Harlow you could never be sure, although she also specialized in Good Bad Girls, as in “Red Dust.”
Harlow was a huge star. "Libeled Lady" from 1936 or 37 featured Harlow, William Powell, Spencer Tracy, and Myrna Loy, and she got top billing.