I would be grateful for advice on whether to visit Mendoza or Cordoba from Iguazu for 3 nights, after Antarctica cruise and before 3 nights in BA.

Mendoza. You will not regret it.

Mendoza, no doubt about it. Enjoy!

A third vote for Mendoza, but then I have not been to Codoba and have heard nice things about this city too.

I've been to Cordoba, but not Mendoza. My sister in law and family live in Cordoba and I was there for two months a few years ago (first trip to Argentina).

Cordoba is a very big city, lots of history, mountains nearby, but it didn't strike me as a tourist destination, especially if you're only going to BsAs and Iguazu.

But, having heard about Mendoza and wineries, etc., I'd recommend going there over Cordoba. Or go to Salta. I was there for a week and loved it (Andes, Incas, wineries).