The only thing I can say for a representative system, such as a Republic vs a Democracy is that in a Democracy, everyone turns into factions, majority rules, and stomps on the minority, whereas a Republic will protect the minority's interests - at least better than a Democracy.
Democracies also vote themselves money until the entire society collapses on itself, landing in, usually, some sort of totalitarian system.
^This^ is true if there are no controls on taking money. Sure if everyone is taxed, they want their money back. But when you have to actually contribute to get paid, it doesn't collapse. This is a fundamental uniqueness with the current Dash voting system. Budgets get voted in only if masternodes have confidence it will improve Dash. There is always the threat of no votes, so it is a self correcting system.
Pretty much every economic system is controlled by the top 100 richest people/corporations. Even the best governments have been bribed to get certain laws/benefits passed growing government until it collapses. It isn't anything new. Is there even any democratic system in place anywhere?