Argentina had pegged its own currency to the dollar. It still had its own currency the Pasco, so when things got messy and they defaulted they just unpegged their currency to the dollar. Yes the value plummeted to a mere 30% of what it was worth prior to the default but a depreciating currency has its benefits too. When a currency depreciates in the world market, its goods are cheaper to other countries so consumers buy their products (soybeans, wheat) and Argentina's exports increase. Boosting the economy helping it recover slightly and giving some investors courage to invest in the Argentina's economy again, all be it at a much lower volume of funds prior to the default.
Greece doesn't have its own currency it's a member of the European Union and a member of the Eurozone, whose currency is controlled by the European central bankers in Frankfurt. Argentina is a sovereign country whilst Greece handed over some power to join the EU like every other member; EU law Trumps national member laws.
However with the new hardline Government elected in Greece, saying they would not pay any more to their creditors, was beginning to look at lot like Argentina in 2001. Through very heated negotiations with its creditors the ECB and Germany it has managed to gain further funding (well a continuation of its present plan which runs out in a number of months, this was the 240billion euro bailout a number of years ago.) But the move by the newly elected Greek national party seems to have pulled the wool over its voters eyes and lay a smokescreen, deceiving them as saying they would not pay and get a right down on their debt. The deal they returned from negotiations with is literally the same deal they had with different names on some of the phrasing of the contract.
I would say Argentina was bolder and turned its back on its creditors but I believe it had more of a chance to do that because it had its own currency and was a fully sovereign nation not a aligned to any EU, it didn't share a currency with 20+ other countries like Greece is doing.