A full transcript with interleaved slide images takes a few minutes to read at most, and lets you control the pace of information absorption. A video with slides, especially when you cannot 2x the talking speed, is a painfully slow data transfer method.
Video + Slides = analog modem
Transcript w/ embedded slides = Google fiber :-)
Of course, if you're into audio books instead of reading, maybe you consider that a feature.
// I push video for a living. It's great for visual explanation like DIY instruction (e.g. woodworking, swapping RAM on a Mac Mini), emotional content, personal story telling, etc. Systems architecture is generally not in one of those categories.