Just to add some more data points.
I ended up going with semi-metallic pads after additional research. Based on the weight we are carrying around, it seems they are a better option for the Westy over ceramic.
That being said, I first ordered Pagid pads (front: 355005391, rear: 355014401) that another Sprinter owner used, and said had good ratings. However, when I received them, they were not rated as advertised. The rears were "GF", which is very good, and the fronts were "FE", which is not as good. I returned them as I wanted minimum of FF on all pads.
I have since ordered front and rear Raybestos pads, with the following part #'s. They should arrive later this week and will post and update once they are installed.
Front: SP1136TR $41
Rear: SP1006TR $47
These are their specialty truck pads, and when I called in, both the front and rear are rated at "FF", which is what I wanted.
I also looked at ATE pads, which also seemed like a good option, all rated at FF (Front: 355014401, Rear: ATE: 607084), but they were more $$ then the Raybestos.