Since most of the 2wd is difficult to get parts in Hong Kong except Team C which ...
ya, true. cannot speak for the RM as I only had few runs with it. But for the Firebolt DM I had it for over one year already with hundreds of runs. I only broken one arm mount and one idler. So I think it is a very durable car.
I can see the plastic materials are different. And the chassis is one piece so more durable now. I think it is different design as the DM have more steering which is better for carpet. The RM have more rear traction which is better for loose condition like dirt or clay.