Looking at the information and road names offered, it looks like I will be going for the Santa Fe unit.
IF this engine runs half as well as the S2/S4 it will be a winner. The S2 with presumably the same drive train as the new NW2, is by far my slowest/smoothest operation engine and that includes my 3Rd rail, MTH, and other Lionel engines. This IS the hot set-up for a switching type locomotive.
The one thing that is a slight disappointment on the S2 vs. all the other engines is that the sound is not a "full" as the other engines as I have and that makes sense since there is so little room in the body.
As has been noted, this is not the LionChief engine, but rather a new engine from the ground up.
Charlie