The ES44AC engines are as nicely detailed as the SD70ACe models Lionel originally produced, although they do lack the grab irons on the top of the front plow, which do appear on the SD70ACe engines. All ES44AC engines are based on the Norfolk Southern bodies with the headlights above the cab windows. (This annoyed me enough on the two BNSF models I have that I used GOOP non-permanent adhesive to attach a twin sealed headlight fixture from B.T.S. to the nose indentation and added MV lenses. The headlights are non-functional but do make the locomotive more realistic despite the appearance of functional headlights above.)
I replaced the couplers with Kadee couplers, so I can't comment on the action of the electro-couplers. Slow speed response is as good as that of the SD70ACe engines, and the revised wheel arrangement means that there are no electrical contact losses and stalling crossing American Models switches. The horn sound of the first Norfolk Southern ES44AC engines is slightly different from the later BNSF horns, but the engine sounds are identical and differ greatly from the EMD SD70ACe models, as they should. All of these locomotives operate as expected under Legacy control. Consists are easy to set up and operate in the Legacy mode.
DC operation, however, is a mixed bag. Like the Y-3, the engines are a bit quirky when operating under DC. Things are usually fine, but sometimes the engines simply sit idle even when the voltage is raised to 10V. This happens to the SD70ACe locomotives, too; but I find they respond more quickly and consistently to DC current than the ES44AC versions. All seem to respond more reliably to the reverse direction than to the forward direction for some reason. When running a consist with DC current, differences in response and speed are obvious because the pivoting pilots might be moving right or left as a trailing engine runs slightly faster than the leader. In general the locomotives even out speed differences; but in the Legacy mode I do not see the differences in speed pushing or pulling the pilots that I do when operating in DC.
Engine sounds respond very quickly to changes in speed from the Legacy Cab unit, but under DC power the engine sound lags seconds behind the control changes. This can result in the engine sound increasing in RPM even after the locomotive has actually stopped. It's a slight annoyance, but the ability to run either Legacy with its finer control or DC is a big plus in my opinion. Overall I do not think there is a substantial difference in operation between the SD70ACe and the ES44AC locomotives except for the better wheel arrangement for the latter. I'm happy with both, now that I put the correct nose on the BNSF engines.
