I'm from Brazil and I see you are from Chile: a 3-hour flight would get you to São Paulo or Rio de Janeiro.
São Paulo is a vibrant city if you like metropoles, there is a lot of diversity and many options for a tourist: museums, interesting neighborhoods, fairs, shops, excellent night life... And much more!
Rio is also a metropole but it seems to be "slower" in comparison to Sao Paulo, because there is also the beach - many beaches actually - and the native forest inside the city itself...
My city, Belo Horizonte, the 3rd largest in Brazil is also an interesting destination and less touristy...
In Brazil there is a lot of diversity, so you can do many different things here: a wonderful beach in a small village in Bahia, you can visit the Amazon Forest, which is such a nice place - the North of Brazil - I've been there and I was very surprised (in a good way), you can go to national parks if you like nature, you can visit colonial cities in my state Minas Gerais... I could spend hours writing about what one can do/visit in Brazil...
The advantages are many, I just thought about the language issue, since we're on italki: you can easily understand Portuguese because you speak Spanish and you will also be understood if you speak Spanish to someone here... It's a country full of cultural traditions and history and the beaches are wonderful... just to name a few advantages
The disadvantages are maybe the price of things, it's not so cheap to travel here and things aren't cheap, I went to Chile, maybe you can expect to pay the same or a bit more, depending on where you go... And there is also the violence, which is an issue in big cities, specially in wonderful Rio de Janeiro... But it's not like they show on TV, like that everywhere is dangerous... Not at all... Maybe just a bit more violent than Chile or Argentina... Well, I think I wrote enough. Write me a message if you want more tips! :)