Probably Warren, with the African-American vote being divided between Booker and Harris.
I think the black vote would have been united no matter what would have happened. Look at how divided they were this time until Jim Clyburn endorsed Biden and he won SC.
I can easily see Black men backing Booker and Black Women backing Harris (the lure of having the first female President and another biracial President might be quite strong.)
Um, no. Outside of NJ, Booker doesn't have much appeal to Black men nationwide. He's viewed as a "softer" version of President Obama. Also, the fact that he's unmarried wouldn't help him either (being married to Michelle did a lot of wonders for President Obama).