1. If I had to live in London or Mexico city, I would choose to live in London for the following reasons. There are fewer people living in London than in Mexico city, so the city won't be too narrowed. Necessities such as electricity or water are supplied better in London. Morever, murder rate is also much lower when living in London.
2. The worst city to live in is Mexico city, where the murder rate is the highest and the clean air is the worst of all.