The KEY BB was a more detailed and refined model than any of the KTM built BB's, but it was also more fragile. KTM built locos were more robust and forgiving in the handling department.
The exception to this was the KTM/USA models that KTM imported under their own name in the mid to late 80's, after the brass train market moved to Korean, due to high cost of Japanese craftsmanship. These KTM/USA locos had all the robustness of the KTM line, but were decades ahead of their time in exquisite detail, running ability and innovation.
They had coasting drives, equalized suspension on the drivers that transferred back to the trailing truck, all axles sprung and had ball bearings, all hatches opened, an opening smoke box door, functioning boiler steps, sliding cab windows and full cab interior with hinged doors and working door handles. In fact, all hatches and steps have working latches (brass wire shaped like handles) to hold them closed. Working headlights, marker lights, number boards, under walkway work lights, cab lights, back up lights on tender and so on. They really were ahead of their time and stand up well to even the latest and greatest imports today except they don't have sound and DCC control. Real collector pieces. They made some FEF-2's and FEF-3's and some BB's.
Butch