Autofocus systems have evolved rapidly since the technology first emerged in the mid-70s. Understanding contrast detection, phase detection, and dual-pixel is a complex business, but might be critical to choosing the system that best suits what you shoot. This intense video covers pretty much everything.
If you're unfamiliar with how the various systems work, sit tight; this comprehensive video from Gerald Undone runs through the processes behind the various systems and explores their various advantages and disadvantages. In addition to a surprisingly interesting history lesson, you should also emerge with an understanding of which system best suits your subject and style of shooting, both for photography and for video.
Gerald references three very different cameras when explaining the various systems and their latest implementations: the Sony a7 III, the Panasonic Lumix G9, and the recently released Canon EOS R. Mirrorless technology has seen a significant change in the potential for autofocus, not just in speed and accuracy, but also in additional features such as tracking and eye/face detection. If you're pondering a move away from a DSLR, it's well worth investigating autofocus before choosing a camera.
As with many aspects of photography, there's no one-size-fits-all solution, and there's no simple argument as to which system is best. Instead, there are different options that might be better or worse for what you shoot, with different manufacturers choosing to prioritize certain elements over others. Do you need accuracy or speed? Do you need smooth transitions or better tracking? Or do you need something that is the best of both worlds?
You might want to plug in the headphones and take some notes as the sheer amount and rate of information here is a little intense.