Many structures, features and dynamics, along with better villagers and overall, quite fun. There are many defense structures and weapons to defend yourself along with some new creatures and items to stand against the parasites. There is some horror aesthetic, and it will be hard to survive. Lost around 30 hardcore worlds with this trial and error. I think this is what testing has summed up to.
Battle- zombies are a lot more built like the walking dead, parasites will eventually be the leading cause of downfall, escape them or fight them. You will have many baubles and various enchantments to help you along with defenses such as auto turrets.
Building- There is some machinery and bigger chests that you can craft.
Landscape- There are many rivers and realistic generation along with tons of new biomes and ruins to explore.