Hi,
The Santa Fe Alco is an Atlas RSD 4/5. Your original question concerns the RS-1. Atlas has produced numerous runs of this locomotive over the past decade or so. Along with the obvious physical differences, they differ mechanically from the RS-3's and 4/5's in that the frame on the RS-1 is cast metal. Consequently this locomotive is a much better runner and will pull more than a similar 3 or 4/5. That's not to say that the 3, 4/5's are poor locomotives, quite the contrary, all these drives were Kato designed and all perform exceptionally well.
I have seven of the RS-1's from various past runs and they all run like a swiss watch. The more miles you put on them the better they run.
Atlas is supposed to be doing yet another upgrade on this locomotive soon with separate grabs and decoder equipped.
I also have two Kato RS-2's and these are the finest running engines I own. They are a bit difficult to disassemble compared to Atlas RS's but once you learn the secret to getting the shell off, I called Kato direct, they too are simple to perform maintenance on. You won't be dissappointed with any of the Atlas RS's and Kato RS-2.
Life Like has announced a P-2000 RS-2 soon so the choices are many and all fine locomotives.
Regards
Don