...
The changes to the terrain are very subtle (with the exception of dungeon terrain which has a more tan/sand color than the blueish grey it used to have).
Grasslands are a bit more tame (again) and lower in terms of grass height
Cobblestone in towns is different mainly in stone placement (you really need side by side shots and a good eye for this one)
Underbrush is sharper overall
Water is lighter blue
Looks like flagstones are simply clearer and fit together a bit more smoothly
Also there seems to be a bit of an improvement across the board due to the Hues.UOP changes. Just a little color tweak here and there helps sharpen up details on a LOT of things.
Then the zoom factor which isn't really helpful to show screenshots, you have to test that one out in the client itself.
Here's a three way comparison of KR vs EC pre-Pub-73 vs EC Pub 73 for the grassland terrain:
Cobblestone pre-Pub-73:
Cobblestone Pub 73