The original Chain drive weavers were the best running. The single motor drive avoided the two motors fighting and jerking like they do in most 2 motor diesels especially at low speeds for switching. I like the chain drives, they are smooth and if properly setup, very quiet and powerful.
As to quality, you need to define what quality means to you. To me it is being as close as possible to prototype dimensions and shape. I am not worried about how many accoutrements it has tacked on, those are features and can be added later. If the base model is not right, then why bother with all the other stuff.
If you are running on very tight curves, you probably need pilots attached to the truck rather than fixed pilots.
As to RS1 vs RS3 they look very very different to me. The RS1 has much more squared off hoods and overhangs on the cab roofs. It basically looks like an Alco S series switcher with a short hood added. The RS3 has more rounded hoods and the cab roof curves into the sides with no overhang. the RS3 is postwar loco, while the RS1 was released in 1939 I think.
The prototype RS1 used 1000 HP 539 prime mover. The RS3 used a 544 1600 HP prime mover. The RS1 was the forerunner for all the road switcher type locos by all builders.