Oops, now I am confused again. Are the local adjustments made early or late in the pipeline? If late, what is the technical advantage of doing them in ACR rather than in Photoshop?
I guess I'm confused as well. What do you mean by late? It seems we've established it is incorporated into the RAW conversion, not applied post conversion and before tiff creation, which would be the equivalent of doing it in PS. As long as it is in that conversion it is different than PS.
As far as technical advantage, it seems to work really well, the engineers think it is better (or as good), and I've seen no evidence it is detrimental.
There are obviously some things that are still easier in PS, and extensive brush work in LR and ACR seems to get laggy so I sometimes use PS as well. From a convenience and storage saving perspective, these adjustments are amazing, so even if the results are identical, it still a terrific feature.