Melanotan makes your skin react to light more effectively and you can get a full tan quite quickly with it (even in a few days). I don't know whether that means it ages you less because it takes less UV exposure to get a good tan with it or if it has some other adverse side effect. But I have tried it once and it is definitely effective.

I assume both is unhealthy, but I also like to be tanned and take the risk. Preferably from safe sun, but when not possible I’m debating tanning bed vs Melatonan and I haven’t found evidence.