Argentina is a single country. SEPA covers 27. How long do bank transfers from Argentina to, say... Colombia take? I honestly don't know, but I'm going to assume longer than they do between EU countries.
BTW, Argentina also had many local banks in different regions. The EU region is just ~1.5x larger than Argentina.
Argentina: 1 country. 1 currency. 1 law applicable to the entire country.
SEPA: EU + Iceland, Liechtenstein, Norway, Switzerland, and the United Kingdom: 31 countries. 12 currencies (7 currencies in the EU alone [1]). 31 different laws (while EU countries must adhere to the overall EU laws, they are free to implement their own laws as they see fit within the general framework).
wslh: yes, yes, they are entirely comparable, after all Argentina also has regions.
[1] https://en.wikipedia.org/wiki/Currencies_of_the_European_Uni... Turkish Lyra is used in Northern Cyprus which, while de jure part of Cyprus, is not in the EU.