It depends on where you want to go. If you just want to visit the south of Brazil, a car is a good choice. If you just want the highlights (capitals and main cities), you should book flights. Buses are not a good choice for long trips in Brazil and there are no passages trains. over 3 years ago
A car is a very bad choice unless you have a satnav. Smartphones are a problem as 3/4G coverage in the countryside is sporadic and Google maps don't allow Brazilian maps to be saved; something to do with copyright, I believe. Signposts are not reliable or consistent and there are few good maps available. The major intercity highways are death traps with large trucks behaving like rally drivers. I would also avoid taking a car into the major cities. Even if you can park at your hotel there is nowhere to park at your destination. Car parks are expensive and on street parking is controlled by the flanelinhas who will damage your car if you don't pay them. Take a taxi in the city, it is easier and probably cheaper than car rental.
The long distance buses are good and reliable but distances can be enormous. Flying is the only realistic choice for many journeys. I travel up to about 500km by bus.
Driving in Uruguay is much easier, better roads, better drivers, shorter distances and smaller ciites. over 3 years ago