To take the opposing point of view...there's no doubt that darker skies result in better images, certainly with similar amounts of capture time. However, it's also true that, if you can set up in your backyard, you can usually capture for a longer time than if you're traveling somewhere, setting up, staying awake there, shutting down, driving home. So, I'd say an alternative comparison might be to give extra time to the light-polluted skies.
For instance, I can shoot a target for several nights (if the skies are clear) from home without much effort. If I drove down to Pinnacles, I might shoot for half a night (unless I rented a place down there). Perhaps compare 15 hours of light-polluted images vs 3 hours of dark sky shots? The exact numbers will vary according to your personal circumstances.
I think the bottom line is that one can capture a Rosette Nebula image from the Bay Area similar in quality to your dark-sky Rosette given sufficient Bay Area exposure time, e.g. see the quality of the image in Francesco's last presentation. There are subtle details that probably may be too difficult to achieve from light polluted skies, but many reasonably good images can be captured and processed from the Bay Area.