"Speed" appears to be the only improvement over previous versions. It's only slightly larger than previous versions. My Paperwhite 4 is a little pokey especia

"Speed" appears to be the only improvement over previous versions. It's only slightly larger than previous versions. My Paperwhite 4 is a little pokey especially in scrolling through a library, but it's not a big deal and not worth "upgrading." So the bigger question is "Why did Amazon create a new version of the Paperwhite with such marginal improvements?"