James Madison addresses this topic in Federalist No. 10, the tenth of The Federalist Papers, a series of essays that argued for the ratification of the Constitution.
Federalist No. 10 makes an argument for a large, diverse republic by saying that in this type of territory, there can be a larger number of characters and voters than in a small one. This means that electors have more options, and more chances to elect someone qualified. It would also be harder for the candidates to fool a larger electorate.