While what you say is true rich it is also far flung and segmented with Carneros to the east (not technically a Napa Apalacia) all the way up to the Anderson Valley in the north out to The Russian river in the west, literally 1000's of square miles. You are also far more likely to be killed accidently wandering into a marijuana garden at the end of a country road than finding a winery.
While Napa is more commercialized (some would say civilized) it it is also compact, essentially 27 miles long and 5 miles wide with only two lovely highways to choose from, but plenty of back roads.
It easy to reach from the bay area and far higher on the snooty scale of Cobra life than Rio Nido or Healdsburg, and your Cobra will be greeted with enthusiasm and appreciation. Many places in Sonoma County you are likely to be ticketed or even jailed for driving a gross polluter.
You will find a women in Napa take the time to shave under their arms and sometimes even their legs. That is something rare in Sonoma County... Or Santa Cruz, I am quite sure of the latter as I married the only girl in Santa Cruz known to shave daily
Napa also recently opened, Copia, The American Center for Food and Wine. It also features Gerystone, the Culinary Institute of California Campus in St. Helena, The Napa Factory Outlets and was the setting for the imortal 80's movie Howard the Duck.
Napa also posseses something Sonaoma will never have, simply it is perhaps the most beautiful place on earth. I'm not the only one who thinks so.