I agree that both are awesome.
South-East Asia is cheap and I think easier to get around. People speak English when you need it but in South America you really need to know some Spanish. I think South-East Asia is also safer than South America though you'll still be seen as a rich foreigner.
I see you're already in Argentina so you have the benefit of knowing Spanish (I don't know to what extent). If you haven't been to Asia yet then I think that's a better experience for you as you've already experienced some of the South-American lifestyle.
For example, South America would be new to me but other South-East Asian countries would be similar to what I've already seen in Singapore and Malaysia. Sure, many countries there are different and I'd love to travel there but many things would be similar to what I've already seen.