While we can make all sort of arguments and analysis on the cost of living, what did it for me was exactly what you stated..."quality of life". Being in software many of us are fortunate enough to be able to live in the most expensive area in the country. However, it doesn't do a damn bit of good when you're miserable due to all of the traffic, crowds and annoying people who surround you.
Being a native I never thought I'd leave. Now, I'm confident I'll never go back...our quality of life is so much better here in Colorado. I would never suggest anyone move there unless they were single, in their 20's and in the technology space. For that group of people, it'd be a great experience. For us older family types, unless you're a total city person, the area sucks the life out of you.