http://www.humantransit.org/2010/05/seattle-the-end-of-trolleybuses.html
Pros: climb steep hills with ease.
So, for balancing pak sets, give them higher horsepower, and they'll have the advantage in hilly cities.
Pak128 trolleybuses: slow, strong, high capacity.
In Simutrans Experimental, there is a feature -hill climbing- . Relate to that.
For 3.5 months, I lived near the 17/31 markers on Nickerson St near the top of that map. :) Trolleybuses are cool.