I think Warren has demonstrated she doesn't really have the grit or stamina to get into this dirty fight: I feel she has pulled a "Hillary" - capitulate to Trump's bullying whilst still trying to seem tough - and failing.
I agree about Harris - I think her past as a "cop" (progressives hate her carceral prosecutor record) - is her ace in the hole. I think if she plays her cards right she can appeal to the BLM crowd and the "law and order" crowd. She's badass. Warren is not.
Not really a fan of Corey Booker running - I think his reputation as a career politician in the hands of lobbyists will hurt him.
I'd love a Kamala Harris/Chris Murphy ticket.

Joe Biden vs Trump means four more years of Trump, no question about it. Any Democrat who has been in the WH or ran for president before should be disqualified. Hillary should never have ran in 2016: she already lost her primary in 2008, she should have taken the hint. Her ego has had catastrophic consequences.