City Sky-line has a way more people. Each of them has a name (not a sily Train-Fever number), place to live, place to work, family. Kids travel to school, adults to factories. All to the parks. The building tools are better there, change of roads/trains layout is fun. Building in Train-fever is tedious work, upgrading in trainfever is garanteed frustration. More over Skylines has excelent optimization and performance.