Interesting question and one that requires in my opinion quite a lot of thougt, not black or white answer. It depends a bit whether you see prostitutes as victims or sex workers and whether you consider that those who purchase sex are behaving acceptably or not. My own view is decriminalize for the victim but not for the punter and certainly not for anyone who profits from exploitation.
Studies/research in this area show that there is no easy answer and what can seem to be of benefit in one area, such as licenses can be issued to brothels, for example, with mandatory health-checks, which seem like a good idea but, these regulations intended to protect prostitutes. sometimes do just the opposite, according to sex worker groups like the US-based COYOTE