To tell the truth, I'm beginning to doubt the robustness of the Kato style pickup on diesels. I now have a Kato F7 and an NW2 that have worn through the needle point pickups enough that they are unusable. Both loco's have a little over a month of straight running on them. One on a holiday layout and one in our display layout at work. The good old Bachmann inside bearing system lasted till I wore the brushes completely away in the motors, about 4 months. By that time the flanges on the wheels were so sharp they could cut paper.
For somebody that is actually going to run and run these things, the Bachmann systems seems to hold up the best. Keep in mind, that is what those ancient LL GP38's had and I still have examples of those things that run great after 10+ years of hard running (my son letting them run on his roundy round layout for hours at a time).