I'm not sure, as the rebuilt program started under the old regime. Most of the SD40-2s are pretty ratty. The older ones had gone through rebuild, and had nicer cabs. The newer ones were mostly used out west, and had better/ upgraded wheel slip control, for running over the Rockies. Most of these newer ones are what's left.
I had a rebuild, and my crew agreed that they were better as SD40s. I don't think the cab is layed out too well. They are noisier than a SD40 too. I'm not a fan of the rebuilds.
I haven't had one of the GP22eco units yet. I'm on a road job, so we get big engines. Our locals mostly have the D&H GP38-2s, and ex Boston and Maine GP40-2s.