Brazil began giving importance to a serious defensive strategy only in 1958, thanks to coach Vicente Feola. The 4-2-4 system adopted for the first time in the Sweden World Cup was actually a defensive solution that provided against the gaps of the WM. With WM, they only had one centre-back alone in the box, because the two full-backs used to attack without taking care of the defensive tasks. With Feola's 4-2-4, Brazil finally had two centre-backs in the box who were always helped by the tactical intelligence of left winger Mário Zagallo, who used to sacrifice himself in the defensive phase, and by the prudence of right back Nílton De Sordi, who almost never attacked. If Brazil had adopted such a prudent attitude, they could have won the World Cup in 1950, in 1954 and even in 1982, but they missed the chances playing without any logical criterion. In 1982, it was a scandal. They were probably the best team, but they threw away the World Cup in the match against Italy not paying enough attention to the defensive phase - the two counterattacks they conceded were just ridiculous!
On the other hand the Uruguayans achieved almost all their most important titles thanks to their tactical abilities. The proper masterpiece was the 1950 World Cup, but they also made a good impression both in 1954 and in 1970 playing more or less with their traditional wisdom.
What I mean is: ok, statistically Brazil have a better average of goals conceded, but in the historical comparison, the defensive abilities of the Uruguayans appear more evident than the Brazilian ones.