Depends on the situation, sometimes the 460 is faster, sometimes it is slower.
I have the feeling it was the same case as the 8800 GTS 512MB I had before.
They had the product ready to go, however the rest of the 9000 series wasn't ready to be released, so instead they released it as a new revision of an existing 8000 series card, when in reality it was really a 9000 series card.
Nvidia Probably would have released this revision as a 400 series however, timing and the lack of a retail version of the 300 series mandated it come out with the 200 series.