Look at the alcohol market in the U.S.
Or even the tightly controlled Systembolaget [0] in Sweden, compared to the modern markets for cannabis and cocaine.
Tax and regulate lowers violence and increases tax revenue, outright prohibition/making it illegal increases violence and lowers tax revenue.
I do believe "sin prohibition" policies, for not just drugs but gambling, prostitution, etc, are one example of "low-hanging fruit", where there is a noticeably better option that is usually not implemented.
Really, for all trades usually controlled by violent criminals (so everything the Mafia/Yakuza/crime groups traditionally specialize in), I believe that the citizens of a given state will be happier if the trade is controlled by the state and not given over to criminals, which is functionally what "make it illegal" does.
prohibiting things that harm the individual should not be the role of government, IMO. Government, in the liberal/Enlightenment tradition, is there as a protector of your 'rights' to life, liberty, and property. While it has a duty to protect you from things which could harm you (eg junk food/sugary drinks), it also has a duty to let you do what you choose to do, even if it's 'bad' for you (eg eat junk food and drink sugary drinks).
Hence the compromise - you can smoke cigarettes and drink Coca-Cola, but the makers of cigarettes and soft drinks have to warn you beforehand, and the transaction may be more taxed than things like basic foods.