The Steam version of this game is currently heavily bugged, resulting in huge performance losses. There is a simple workaround for this though:
- Put Steam in OFFLINE Mode (Top left, click Steam -> Go Offline...)
Then Start Anno 1800 normally through Steam. It will run just as smooth as the Uplay beta did, and give you a HUGE fps boost. Since your Uplay is still in online mode, you can still play multiplayer games.
My theory is that there is a major issue with the current version of the game querying some SteamAPI calls on every tick, causing huge lag spikes, fps drops, and stuttering effects. The developers will probably fix this eventually, but for now this workaround lets you enjoy the game :)
Important: Do not just go offline in Steam Chat. Use the offline mode. (Top left, click Steam -> Go Offline...)