In Amsterdam, I hung out with a guy who was openly smoking crack on the street and legally got my dick sucked by a hooker. In Amsterdam, the cops will leave you alone, hell, they might test your drugs for you, just so you know you've got good stuff. Drugs are still very illegal in Miami though, even by American standards.
I guess it depends on what you want. Amsterdam is a more walkable city, better public transportation and you can bike around as well. Miami is a tropical city, warm water and beaches, big booties in bikinis. In terms of food, Amsterdam is better for Asian and Middle Eastern, Miami is better for Latin American, Italian and French.
Miami is probably a bit cheaper because of the relatively weak dollar compared to the euro. Miami better for nightclubs and alcohol, Amsterdam better for drugs and hookers, especially legally. You can save money on good food in Amsterdam because you can just grab a kebab or falafel or fries on the street. Then again, you might find a food truck with a nice Cuban sandwich or something in Miami.