I am a fellow Southern Californian and I just visited both campuses last week. I liked Tufts’s campus and downtown more (Williams doesn’t really have one), but the programs at Williams seem very interesting. I’m not going to apply ED to either (I’m doing Brown), but if you haven’t visited the campuses, I wouldn’t recommend ED for either.
These colleges offer two really different environments (pop. Williamstown–7,000 vs pop. Medford 57,000) Go see them both before applying ED, unless your the kind of person for whom your surrounding environment doesn’t matter.