The conquest of the Americas proves decisively the advantage of advanced armor and weaponry in any conflict. The Aztecs and Incas numbered in the millions, yet were defeated by Spanish forces numbering in the hundreds. A heavily armored conquistador could slay dozens of foes in a single engagement without receiving a serious wound. Horses were another advantage that the natives could not counter.
It’s inaccurate to say that the success of the Spanish conquest was solely due to superior arms and armor, however: the Spanish were greatly aided by diseases previously unknown to that part of the world: millions died of illnesses such as smallpox. There was also a great deal of luck involved: for example, they invaded the Inca Empire at a time of great crisis, as a brutal civil war between brothers Huascar and Atahualpa was just ending when the Spanish arrived in 1532. (Link)
Conquistadors, the Fall of the Aztecs (Michael Wood video)
Conquistadors, the Conquest of the Incas (Michael Wood video)
Conquistadors, the Search for El Dorado
Conquistadors, All World is Human
The Great Inca Rebellion (Nova video)