The best current consolidation of the history, new features, and lost features of kindle firmwares is the
Kindle Firmware wiki page:
https://wiki.mobileread.com/wiki/Kindle_Firmware
and its discussion thread:
https://www.mobileread.com/forums/sh...d.php?t=356161
Be prepared to invest some time and thought. As shamanNS wrote, what is better is very much a personal matter, as are trade offs between "two evils". On top of all that, it is a complicated topic.
Note that wiki page also has links to new firmware specific threads for some firmware versions.