Cities Skylines 2 PC performance does not reach internal benchmarks, but Paradox will still release CS2 on time, as we also learn about Cities Skylines 2 mods.
(seemingly) traffic AI comparable or even better than TM:PE
seasons (!)
Actually Useful Unique Buildings
Vastly improved industry handling
More Zoning, importantly mixed use and degrees of residential
Better Custom Industries mechanic (not district based, expanding on the new base will allow for more engaging additions through DLC, Updates or Mods)
Improved Outside interactions (ability to buy/sell electricity for example)
Ability to create outside connections without mods
Finer expansion planning via smaller squares (map size aside I think the squares being smaller is a good thing)
Overhauled city expansion mechanic, you don't have to spam population to unlock new things and you don't automatically unlock everything. Instead you gain points via xp you get through multiple activity sources (you can level up a city solely by building streets for example). The points can then be spent on more advanced buildings of the basic unlocks (highways have to be "bought" using those points after unlocking roads, trains have to be "bought" after unlocking busses, etc.)
Don't forget overall better service pathing (apparently) and the ability to restrict a service to a district. That was one thing I wanted desperately.