Where will most of your customers be? If this is a startup with an enterprise sales component, that's important to know, because you'll be doing sales calls with them (at least initially)
This is the right answer. Your legal entity is best and easiest located where your target market is because that will streamline all of the administrative details that otherwise become possible blockers. Where your employees are isn't all that relevant, that could, especially with today's support for remote workers, be theoretically anywhere.