I've got them all. The metal tracks are really cool and haven't broken a link yet. I ordered a replacement set of plastic tracks once, the ad said they were heavy duty but they seemed the same as stock to me.

With metal tracks and gearboxes the tanks run more realistically, they plow through grass and debris because of the added weight rather then glide over it. Of my nine tanks, 4 so far have metal tracks (the ones we use the most) and all of those plus two others have been fitted with metal gears.

The original plastic gears are ok, never had a problem. Then they came out with the slipper clutch in the gears, this made annoying sound when tank ran into obstacle it could not overcome thus saving the electronics. However, with metal gears and tracks I have yet to burn out a board.