Drums are a maintanance pita, you can go form a simple reline to camshafts/drums/bushes in a heartbeat and the german parts are very expensive.
Sadly we still run drums on the trailers at work, on the upside I only work on the trucks 
The discs brakes basically come in two sizes and with the smaller ones you will struggle come mot time and they run hot hot hot at full weight, the larger discs same size as the trucks are the absolute mutts nuts, but like all disc brake systems if you dont or know how to look after them they can get expensive, on the other hand drums can take some abuse and you will most likely get away with it.
I hate drum brakes with a passion.