The success of a democracy in economic terms may depend on exercising informed choice, however, you must realize that the right to vote is the only powerful political tool that the poorest of the poor people can have. They cannot take recourse to courts as justice is expensive and often delayed / denied. Moreover, if we keep a minimum education requirement for the right to vote, then the poor backward people will never be able to prosper as they will be caught in an endless vicious circle where they will be kept outside of power and the state will treat them as low priority second class citizens (in a system akin to the centuries old caste system).

Therefore, every human must enjoy his right to vote. It is a matter of human rights.