We stayed at the Park Hyatt on our last visit and was duly impressed, it's old and new, retains all the charm of the old building with all the modern conveniences.

Howe about an apartment instead? Great apt and great location - we spent a month there earlier this year

http://www.vrbo.com/142764

I love the Alvear Hotel (Argentine owned) in a wonderful location with nice lobby,fabulous bar with the world's best Bloody Marys and wonderful Sunday brunches - not to mention its French Restaurant, which is great.

Oh, then I also love the Hyatt for it's Teas and gorgeous patios.

What lovely choices you have...

Any thoughts on the Sofitel ??

I think the Sofitel is a wonderful hotel, too. I haven't stayed there, but the lobby is lovely, and friends enjoyed a short stay there.

It is located near art galleries and the small, interesting Enrique Larreta Museum. I do not love the location, especially for a first visit to BsAs, nearly as much as the others mentioned (by me as they are closer to more interesting sites, parks etc.