Andreas Antonopolous is the most common choice because he knows the stuff pretty good at a technical level and is well spoken and can make things viable to watch for longer periods of time, but if you want to learn from a real expert then I recognize that you watch lectures by Adam Back. The guy may not have the speech skills of Andreas but he is an actual developer of Bitcoin so he knows more at a technical level.
Fair comment IMO.
Although Andreas has chosen some highly questionable platforms to speak on in the past, it's not like he's beyond doing good lectures about Bitcoin, I always appreciate and enjoy what he does from a technical standpoint, not just because he's good at "framing" his talks well. I could easily imagine both Andreas and Adam Back doing actual university lectures, but with Andreas more suited to the freshman end of the course material, and Adam handling the final year/post-graduate end of the spectrum.