I have a sunset 2-8-0 that was built back in the 80s with the original belt drive and it still runs fine. As someone said, "if ain't broke, don't fix it".
These drives are smooth and quiet if properly adjusted. I was told years ago, the belts were "the same as the ones used in printers" and will last forever.
The smooth running is one big avantage, probably in part due to having teh motor shaft and the gearbox shaft parallel to each other.
In addition, with this type of drive, the Belt tower can be entirely hidden in the fire box on a steamer, thus leaving the space under the boiler above the drivers open/see-thru. This is very protypical and generally not possible with a conventional gearbox drive. If you look at some backlit photos of steamers, you can see right through between the boiler bottom and the tops of the drivers.
