The airport Jorge Newberry is not that far from Palermo.Eze is a few hours away I think the other place to pay is better near Puerto Madero
But feel free to go to EZE or microcentro migraciones if you prefer.
Now that I've done it, I can say it took longer than I expected because only one migraciones window was open (should I say, only one exists), and someone had a complicated problem ahead of me in the line. They process credit card right there, easy peasy.
Are there many windows in EZE?
Also I'm intrigued by the option of blowing it off and paying online from outside the country, in order to be able to enter again. Anyone have experience with that? If there's no downside I don't know why we don't all do that... Is it a ding on your record?