A tramway can be 50 meters long. A bus is usually 12-18 meters.

A tram system can be fully automated.

An electric engine is more efficient (constant torque) in an urban area with lots of stops.

In countries like those in Eastern Europe, car drivers don't give a fk about buses and bus lanes. But they are scared enough to make way for the trams (if they collide, the tram will barely be scratched while their car ends up totally smashed).

The tram vehicle lasts more time. My town uses 50 year old trams without any issues, while the buses must be replaced after 10-15 years.