Why did the Spanish & English settle in the Caribbean in the 15th & 16th centuries?
Spain settled in the Caribbean, as previously noted, early in the 1500's and continued to expand its empire throughout North, South, and Central America. Although Christianizing the heathen has long been used as an excuse to eradicate native beliefs, the driving force behind Spain's rapid expansion throughout the Americas was indeed gold, after the early Spanish explorers came upon Incan Civilization with its golden artifacts. Sadly, much of these were melted down and shipped to Spain. Controlling the islands in the Caribbean, of course, allowed for a base of operations and helped safeguard Spanish shipments of precious metals back to the Old World. England, which had been at war with Spain, began to infiltrate Spanish outposts, and actually attempted a small settlement in Central America to counter the Spanish influence there in the late 1500's. Additionally, the English fleet began to raid Spanish vessels en route to Europe and take their gold. This began the iconographic era of piracy, which lasted until the late 1700's. After the defeat of the Spanish Armada in 1588, England gained and maintained the upper hand as the world's sea power for about 300 years.
When the Spanish (in the form of Columbus's expedition) came to the Caribbean in the late 15th century, they were coming for "gold, God, and glory." They wanted to get rich by finding gold, they wanted to spread Christianity, and they wanted to get glory (the glory of finding new things).
As more settlers came in, there were a few other reasons for settlement.
First, the islands came to be used for growing sugar. Throughout most of their colonial history, sugar was the main crop of the Caribbean and it made the islands very rich sources of income for the mother countries. The Spanish and English (and French and Dutch) competed for these islands.
The islands were also important because of how rich the mainland of Spanish America was. There was silver, in Mexico and Peru and it had to get shipped to Spain each year. It went through the Caribbean to get there. So the islands were important for Spain to help defend these shipments (and the mainland itself). And they were important for the other countries that wanted to try to capture the shipments.
In addition to the answers provided to you previously, these are other reasons why the Caribbean was a good place to anchor a good part of their presence.
As far as the Antilles, their strategic position was prime for trade, natural resources, the creation of forts, defense, and war strategies. Spain, under the ruling of the Kings of Castille and Aragon (Fernando and Isabel) was responsible for affronting the money to Cristopher Columbus in the expedition that came to be known as "the discovery of America".
The resources that were found in the Caribbean were nowhere compared to those found by Hernan Cortez, but the availabilty of three different bodies of water (Caribbean Sea, Pacific Ocean, and Atlantic Ocean) surrounding these islands definitely proved beneficial for the establishment of new trade routes.
The same thing happened with the English as they began to establish their own trade routes once the colonies started to build a trade economy.
The first attempt at colonization was made on Roanoke Island on the coast of North America in 1585, by Sir Walter Raleigh. The settlement did not last, and England will not have any tentative exploration and colonization in the Americas until 1604, after the peace with Spain.
In 17th century, Great Britain established the first empire, which had its center in the western hemisphere, ie the Caribbean islands and North America.Settling down in the Caribbean was holding Empire strategic naval superiority.It began with the establishment of tobacco plantations in the West Indies and religious colonies located along the coast of North America.
To become a great power, a country must meet three conditions or criteria. First, countries must be the neighbors of worldwide oceans, on considerable length and have access to oceans by an opened sea. Second,countries must not have powerful neighbors in the immediate vicinity. Finally, they have to have a naval capacity and high military potential of the sea fleet. All these three criteria were met by Britain. Geographic position of this country, combined with its naval force, have secured for Britain the role of world power that it held so long. Both acquisition and especially the preservation of the British Empire, were dependent on ensuring control over the oceans.