I believe people have a hard time understanding why decriminalizing sex work is better than legalizing it because they first hear those terms in reference to marijuana, where respectable activism has long centered buyers rather than sellers.

Decrim from the perspective of consumers means less protection. Firstly, because striking down criminal penalties doesn't protect you from civil charges; towns can still fine you. Decrim may be a first step before striking down civil penalties, but both processes take time.

Legalization, on the other hand, immediately frees consumers from penalty by shifting the full burden of legal compliance onto the seller. This is great if your entire interest in marijuana or sex work is that you want to pay for products and services you enjoy.

If your interest involves your right to earn a living by selling these things, however, your protection from state prosecution is conditional on your being able to pay for and document compliance with state regulations. The most marginalized sellers remain criminalized.

The second way that legalization protects consumers is through regulation itself. Though marijuana is a terrible example, it's reasonable to want the state to enforce accurate labeling and safety evaluations of products that can kill you. Sex is a thing that can kill you. However

sex workers are not things. There is no way to regulate sex work without violating sex workers' rights to bodily autonomy. State regulators are, like cops, also human, and not all to be trusted in positions of authority over a sexualized class of marginalized people.

From the seller's perspective, either option is better than full criminalization, and neither guarantee full protection. But decriminalization is the better route, protecting all workers from the worst penalties and state abuse.