I have an NJCB RS1. It is a very nice runner also. My has gear towers, I think instead of the chain and sprocket drive. All Nation did produce the for a line of NJCB engines at that time. The detail is not as fine or as much as more modern locos but is good as it is. I would recommend it.
I have not seen a Carworks version, but I have a Carworks Baldwin VO1000 switcher. It is nicely detailed and runs well too. It has a Weaver drive. I don't think the detail is at a higher level than the NJCB RS1 however.
So either would be a good choice depending on what you find. They do show up ar various 2 rail train shows. The big March Meet in Chicago (Lombard) next march would be a good place to shop.
Another non-brass choice is the Atlas O version. I have seen some of these run and they seem to run pretty well also. However, to me they look oversize for O scale. I have never measured one to find out if that is true or an illusion.