Voice A feels clear, but the engineering makes it feel more like it's about to throw a trailer for the next blockbuster. Voice B feels old-timey, like I'm listening to an audiobook in a vinyl record. Voice B is the one I like the most. That sound suits educational stuff better; it's less performative and more conversational.
I also prefer voice B. For some reason voice A just immediately made my brain go "American Science-Bro, be sceptical!"
My apologies to our American friends, I think I've just seen too many influencers peddling scams and pseudoscience :')