[eschaton]

IMHO, it's not so much a question about residential versus office being better but that if you want to have the healthiest business districts, you need a balance of both. An area too strictly residential will be sleepy/dead at any time except the evenings and weekends. An area too strictly office based will be dead except around the lunchtime rush. Add both together and you get a more relatively constant number of people out walking, which creates a steady daily revenue mix for local businesses, and probably helps certain types of businesses consider locating there which might not have otherwise.