I think it's wise to ask the question: Where do I/we need to be to build the best team, or the best company?
Are you in a domain where you need to hire people that are difficult to find outside of Silicon Valley? If that's the case, it makes perfect sense to found in the valley.
Is your business capital-intensive, and funding will be a long-term concern? Maybe SV or NYC makes more sense.
Are you entering a domain where most of your key customers will be located in specific metro area, and being located there lends you credibility? Found there.
It may also be smart to found where you have lots of local connections, letting you staff up with vetted local talent and leveraging local connections to get introductions to potential customers.
And finally, founding close to family/friends can help keep your mental health in check and help you stay focused.