From my usual side-by-side comparison (slow but comprehensive), the only significant changes to the settings are the addition of -protecthalfops and -autohalfop to global-chanset. There has also been a lot of cleaning up throughout (mainly in the descriptions).
I've found the UPDATES file itself practically useless for tracking config file changes, and deficient for tracking general changes in eggdrop.
I agree ... UPDATES1.6 is useless for tracking where changes happen, etc ... I think starting with 1.6.13 I am going to use a ChangeLog style like we do w/ eggdrop1.7 ...