Which of the following explorers would you consider most significant to the age of Exploration and why?Cabral: Reached Brazil and claimed it for...

I'd have to agree that Magellan remains the most important out of the group you list.  His voyage proved conclusively what Gautier de Metz wrote in L'Image du Monde in the 14th century, that a man could make a journey around the world "as a fly makes the tour of an apple."  I'd have to point out, though, that Columbus, as vilified as we was late in life, was certainly the most important of early Spanish-Portuguese explorers for having been able to mount the first major voyage across the Atlantic and into the unknown.  Despite earlier landings in the New World over a period of centuries by some variety of others, he was the first to do so with the blessing of, and in the interests of, an actual nation-state which could follow up on his success.

The link below leads to an account of the voyage around the world begun by Magellan in 1519, written by a Portuguese who was a pilot with the expedition.