Hi. Everyone has their own opinion, so I'll give mine too! I have a "pre-pago" with Swiss Medical and have been quite happy with the medical attention. They have top doctors and excellent facilities. It is a costlier plan than most, but you get access to a lot. I recently had an operation (my foot), and was operated on in the Sanatorio Agote (built by the Clinica Suiza) and was impressed by how professional everything was, not to mention that the hospital room was like a 5 star hotel! I had my own "suite", it was very quiet, immaculate, and could even choose my dinner from a menu. Those things I know are trivial BUT it did make my stay more comfortable, and above all- my surgery went very well and I am recovering well.
There are excellent doctors in Buenos Aires, so I wouldn't doubt having an operation here, esp. one that is fairly routine. I also had a baby, then lost a pregnancy,- all here- and I had no complaints about the medical attention.
There is also an "international" center for foreigners who do not have a pre paid health plan, but I don't recall the name. The doctor who told me about it, and is associated, has the surname of Cohen, if that's any help...
Good luck!!