Same differences as between SG freight and passenger trucks.
Some basic differences: The kind of springing and equalization between the axles. Also passenger car trucks will have swing motion bolsters more often than freight cars. The reason is to provide a smother and more comfortable ride for the passengers.
The passenger car trucks will have a different appearance.
This detail of a photo I took last August on a rainy day in Silverton will give you the idea of how different a passenger car truck is from a freight car truck:
Brian Norden