It is not just having diverse restaurants however,as we have learned. When moving to our little town in Virginia after living in California for 50 years with the last 30 in SoCal, we did not realize how spoiled we had become to having truly good, authentic ethnic food really close by at very reasoable prices.
We have lots of "diversity" in restuarants even in our little burg -- two Indian, one Thai, two Chinese, two Japanese, several Mexican, two Italian. Pretty impressive for a county of 50,000, but they are all pretty mediocre. We think it may be because the local palate can't really take the ethic flavours of authentic cooking so the restaurants have tone it down to almost nothingness, but it has been a major disappointment.
So, I determined the biggest benefit to living in a truly large city is the authentic ethnic food you can get and get fairly close to home!