https://www.nbcboston.com/news/politics/decision-2020/study-finds-stacey-abrams-is-bidens-best-choice-heres-why/2094483/
Biden's main argument is that he is competent and will return things to normal. Veep isn't terribly important, but he is old so people want some assurance that his VP is ready to be president. And I wouldn't say that about a person who never won a state office. I could see GA being appealing, but someone like Kamala Harris has been on the national stage and seems a lot more ready, if you want a black female.
I'd also prefer someone who has national campaign experience and has been vetted. A lot less surprises that way.
Plus if Biden wins he's likely a one-termer and his Veep becomes the presumptive frontrunner for next election. I'd rather the DEM front runner be someone with a solid resume who is ready for the next election, than someone who is largely new to the national stage and could be a weak front runner (kind of like what Obama bequeathed us).
Kamala seems the obvious choice. Successful, tough, well-spoken, national campaign experience, her senate replacement will be another Dem, etc.
A black woman could help patch together the Obama coalition that Biden is counting on, and potentially fire up the base.
The other main contenders seems to be all from around the midwest --Amy and the two Tammys. With Biden trying to project steadiness and competence, going for an unknown/lesser known surprise addition to the ticket seems like the wrong move (and usually will be).
Just to make up numbers, i'll go with:
40% Kamala
25% Amy Kornhusker
10% Tammy Baldwin
10% Tammy Duckworth
1% Liz Warren
4% someone else
Okay, my Someone Else # should be larger. And Abrams probably has at least a 10% chance, that I'm discounting.
But I think those 4 are the faves.