In 1763, Spain traded Florida to Great Britain in exchange for control of Havana, Cuba, which had been captured by the British during the Seven Years' War. wikipedia
Why did Spain trade Florida to the British in exchange for Havana? Florida is much larger than Havana, and Spain still controlled about 80% of Cuban territory.
The wikipedia page on Havana clarifies
Less than a year after Havana was seized, the Peace of Paris was signed by the three warring powers thus ending the Seven Years' War. The treaty gave Britain Florida in exchange for the city of Havana on the recommendation of the French, who advised that declining the offer could result in Spain losing Mexico and much of the South American mainland to the British.[19] wikipedia
The basic "settlement" of the Seven Years' War (called the French and Indian War in North America) was that Britain would get all of North America east of the Mississippi River. France gave up "East Louisiana" (the territory between the Mississippi and the Thirteen Colonies), while Spain gave up Florida.
In return, France got to "park" the main "Louisiana Territory with Spain (until Napoleon took it back), and Spain got to keep Mexico. Britain gave back Havana to Spain to "round off" the deal.
The better question is why did Britain exchange Havana for Florida? I think it is because Britain (for example, the Prime Minister Lord Bute) knew they could not keep Havana in the long term since it was only a matter of time before it was recaptured by the Spanish criollos, just like Buenos Aires would be 40 years later.
