Infrastructure: Undoubtedly Dubai has the best infrastructure. Roads are wide and smooth. Metro is operational at both the places but Dubai's metro network is bigger in comparison. Traffic congestion is still an issue at both the places. Traffic sense in Dubai is a lot better. Mumbai's infrastructure is improving but it's still a long way to go.
Shopping and Entertainment: Dubai has the biggest mall in the world. However, it's relatively expensive because the goods are imported from other countries. Mumbai caters to all class of people ranging from hawkers to branded showrooms. Dubai has great amusement parks, gardens.
Weather: Dubai has extreme hot & dry weather during summer and relatively cold during winter. Mumbai's weather mostly remains hot and humid throughout the year.
Jobs: Both have good job opportunities. Wages are higher in Dubai due to higher GDP. The major advantage in Dubai is that you don't have to pay any taxes so people living there save a lot of money.
Cleanliness: Dubai is a lot cleaner because the rules are very strict.
Culture: Dubai is multicultural country since most of the population consist of expats and people from various countries. Mumbai also has diversity but mainly from different states in the country.
Food: Food is much more expensive in Dubai because it's imported from other countries.