Trams are more comfortable for the passenger, as the ride is smoother. It's on rails, so no bumps, and acceleration/deceleration generally doesn't have abrupt jerks.
On the other hand, buses are far more flexible; a minor glitch like an accident or someone unloading their moving goods stops a tram on the street totally, because it absolutely doesn't go round any obstacle. Buses do.
It's very small still, of course, but seems to progress without major problems. (They make a point about the exceptional arrangement for the risky investment, i.e. the municipal company bought and operates these buses themselves; normally they just organize the procurement of transport services from private companies who own the buses and hire drivers.)
On the other hand, buses are far more flexible; a minor glitch like an accident or someone unloading their moving goods stops a tram on the street totally, because it absolutely doesn't go round any obstacle. Buses do.