They're more expensive but I think they last slightly longer. In my experience they're a much more pleasant ride because they're quieter and don't vibrate as much. They're also much quieter from the outside, which I noticed when a route in my old neighbourhood converted to diesel. But there are lots of wires so I suppose some would say you have to balance the sonic effects against the visual.What exactly is the benefit of trolly busses vs. traditional busses, other than the lack of local emissions and lower energy costs? The only thing I can think of is faster acceleration and more torque due to the electric motor and rubber tires. Furthermore, once the technology in battery powered busses improves, trolly busses will have no benefit over them other than perhaps the lack of expensive battery swaps every few years. I think we're better off holding off on trolly busses until battery powered busses have matured.
The torque thing may party explain why hilly cities out west like them.