Of course it all depends on how you define quality of life but overall urban living offers a better quality of life.The urban life offers many opportunities for cultural advancement as well as proximity to shopping and places of employment.This way you don't have to worry too much about transportation.
In the city, there is lots of noise and mainly restaurants, office buildings, and parking lots. In the suburbs, there is mainly houses, schools, and sometimes parks. Suburban people generally have more space and therefore more room for stuff. You are supposed to have commercial property in the city and then private homes outside the city that way there is a clear divider than lets people have more peace, tranquility, and better air quality.
Life in the suburbs is better than life in an inner city. There is more crime in the middle of cities. There is also more traffic, noise, and air pollution. The suburbs are more suited to residential living. Usually, rich people choose to live in the suburbs because they are safer.
Suburban living offers a better quality of life, because there are so many people in cities, that they are dirty and it is stifling. In the suburbs, you can own a 3 bedroom home for the same cost as a one-bedroom efficiency apartment in the city. In the suburbs you don't feel like other people are on top of you.
Suburban living offers a better quality of life than urban living does. Urban living usually means living in neighborhoods that are not well off with little protection and many people around who would mean to do you harm. Suburban is usually better security and less people around who would mean to do you harm.
A better quality of life is a relative thing. Everyone has different ideals and things that are important to them, and urban and suburban living have their pro and cons for different lifestyles. I've lived in major cities, and in the country, and I've got to say, from personal experience, living away from the bulk of civilization is more pleasing to me.