The good thing about Republicanism is that there is also a chance for a meritocratic system of things, meaning that anyone, regardless of status and class, could advance in society. The bad thing about Republicanism is that there's a good chance that idiots and morons could also ascend into positions of power.
I forgot the proverb, but it's got something to do with ruled by one idiot vs ruled by hundreds of idiots.
Monarchism on the other hand, would provide a long term development plan that will be beneficial, plus it removes the inconvenience of having to change the policies whenever a newly elected leader wins an election. The downside of monarchism is that there is a slight larger chance of stratification of society by class, meaning that the lower class could not advance past their station. Feudalism and monarchism also go hand in hand in this case.
Oligarchy would also be present in both monarchism and republicanism as well.
If monarchism would have to be used, it should be a mixture of constitutional monarchism and the Chinese ideology of the Mandate of Heaven, where a monarch would still have to rule wisely, or he or she will lose that mandate. If only the Russian Tsarist system had adopted the Mandate of Heaven and Christianize that ideology, then Russia wouldn't have idiot or cruel Tsars. Likewise, Imperial Germany would also have benefited from the same proposal I said just now.