There is no question that the greatest democracy will be a more successful and prosperous political system than the worst dictatorship. But if we flip the tables and question whether the worst democracy will be better or worse than the greatest dictatorship, it becomes a very difficult question indeed.
Pictured above is Otto von Bismarck. He is one of the historical leaders that I have the most respect for, behind George Washington. Unlike George Washington, Bismarck was a dictator. He held the role of Chancellor and was officially a subordinate to the Kaiser Wilhelm I, but in truth Bismarck held all the power. As the subject of Wilhelm I, before he became the Kaiser, he was a well respected man but considered as very radical in his approach. Nonetheless, he was a very successful leader and oversaw great victories in the Austro-Prussian War and the Franco-Prussian War, alongside his colleagues Roon and Moltke the Elder. Bismarck's efforts eventually led to the Unification of Germany in 1871. As Chancellor, Bismarck had very popular policies, such as welfare for those that reached a certain age (though the welfare age was higher than the expected lifespan), and was unparalleled in his foreign policy. During his 20 years of power he maintained peace through strength and good relationships that he had built with other European nations. Bismarck can be said to be the greatest dictator in history.
Pictured above is Jacob Zuma, the democratically elected president of South Africa. Zuma has a 5th grade level education, is extremely corrupt, has been charged with rape (though acquitted), was previously a member of the communist party and had been exiled prior to his return to the reformed South Africa in 1990. Jacob Zuma is the worst leader in South African history and one of the most unqualified leaders in recent times. Save your comments about Donald Trump; he completed school and was a successful businessman. The only success Jacob Zuma has ever had is winning a joke of an election. He has claimed the root of all of South Africa's problems, many of which he has created or made worse, on Jan van Riebeeck, a Dutch explorer who colonised South Africa in the 17th century. Riebeeck died 350 years ago and can't possibly be responsible for the problems South Africa is facing.
To make matters worse, Zuma is a notorious racist and believes that white people are a cancer that is ruining his country, despite the history showing that the white people, despite the racism, industrialised South Africa and turned it into the most civilised and advanced African country for many decades. He is a historical revisionist who says what he wants to see, rather than the truth. It is because of Jacob Zuma that racial tensions are so incredibly high, that white farmers are being killed in large numbers, and that whites are feeling less safe than ever. Zuma is abusing democracy by coaxing the black majority into committing acts of violence against the white minority and the whites don't have enough voting power to elect a better leader by themselves. It's not a stretch to say that Jacob Zuma is one of the worst democratic leaders in the world.
My favourite show, Legend of the Galactic Heroes, tackles this question in a serious and mature way. On the right, Reinhard von Lohengramm, is the Galactic Empire's (Space-Prussia) dictator and Yang Wenli, on the left, is a military leader from the Free Planets Alliance (Space-America). I highly recommend you watch this show for in depth politics, philosophy and military strategy and tactics. It's a bit dated but definitely worth the watch.
It can be difficult to formulate an answer on whether the best dictatorship or the worst democracy is better. On the surface level the best dictatorship is obviously superior since it has a strong and good leader, it preserves culture and protects the people. But what happens if the next dictator is someone as incompetent as Wilhelm II, who undid all of the foreign relationships Bismarck had built and was majorly responsible for the Great War? It may not happen immediately, but it would be unlikely that a line of dictators would never have a dud. And when that dud inevitably has power the entire society can collapse with them, just like what happened to Germany after the Great War.
On the flipside, the worst democracy could lead to a rebuilding of society in the future due to the freedoms the people have. If a population becomes vigilant and learned about history and politics, society will thrive. George Washington's revolution lead to a time of excellent politicians. However, it must be noted that George Washington and the Founding Fathers created a republic, not a democracy. A republic has fundamental rules and protections (the Bill of Rights and the Constitution) that a direct democracy excludes. A direct democracy could turn bad more easily than a republic and can lead to a total collapse of society. However, it is worth noting that under many bad dictatorships culture has been preserved, especially in Eastern Europe when they were under Soviet or Nazi rule. Culture is maintained in spite of the state. A direct democracy can't preserve a culture because the rules change based on what culture has become. What 51% of the people want. Even so, a good leader could arise and restore culture, restore order and make the nation great again. In fact, that's what has happened in America after 28 years of bad leadership and failing democracy.
Where does the right balance lie? I don't know. But what I do know is that we the people must maintain constant vigilance.