1. They're focused a lot more on 3D audio this time, and likely VR by extension.
2. They balanced toward lower cost, MS is balancing towards raw power at a higher cost. Lots of (accurate, but also a lot of "so it's really like") talk about the raw figures not being important or comparable.
3. The BC doesn't sound like it's where they promised it would be. They only discussed PS4 so far, and said that at launch most of the "Top 100" titles would be playable.
4. A bunch of custom processors and related hardware to try to smooth out bottlenecks, and for games to use memory and storage much closer to "Just In Time" rather than keeping everything on-hand in case it needs it sometime soon.
5. Some consumer M.2 SSDs will be allowed as expandable storage, but only if they meet or exceed the PS5's. Slot size is also an issue due to large coolers. You can load PS4 games to external hard drives and play them off of those, or import them into the PS5's SSD.