Having lived in the Bay Area, i have had the opportunty to in both hotels. As stated, I definitely lean toward the Sonoma property. In fact, I often use points to celebrate special events at this property. The staff and property are lovely, the cottages very private. There is a tasting room immediately next to the property. If you have children under ten, there is a great train "amusement park" across the street.
You can easily bike downtown or a healthy walk. There are fantastic tasting rooms (one Aussie winemaker not to be missed!) and a very tasty Mexican restaurant.
I scheduled a work meeting for a group of 60+ at the Napa property. I agree with the above poster on that property.