I also have Hospital Aleman. I have myself and my wife on it, full coverage, and costs me about 650 pesos a month, which you can't beat when you think about what you would pay in the States!
I had some friends who had Swiss Medical and the only complaint they had was the price. At the time it was 900 pesos for two, for their best plan, but that about two years ago and my coverage was around 400 pesos for two at the time.
Also, depending on where you are, Hospital Aleman has a hospital in Recoleta which is very convenient. They also have partnerships with many clinics and doctors all through the Capital Federal and the province of Buenos Aires (I'm sure all the medical plans from Swiss, et al do as well).
I pay 10 pesos for a visit to the doctor, and have to pay a bit for and prescription medicine, but you can buy them from the hospital. I was sick with sinusitus about two months ago and it cost me 10 pesos for the visit and 50 pesos (buying at the hospital) for the antibiotics and a prescription spray for my nose.