Dagny and others up thread have hit on some key points. Some things to think about:

What kind of emergencies am I most likely to face? Hurricane? Flood? Earthquake? Wildfire? Chemical spill? What others are perhaps less likely, but still possible?

For each of these possibilities, is sheltering in place a good option? For example in an area subject to severe flooding, evacuation might be the only realistic option. In other locations and situations, if you have made suitible preps, sheltering in place might be a better plan.

How much warning are you likely to have? For hurricanes you are likely to have a lot of warning. If getting out of Dodge seems the best choice, it's probably best to make that decision early to avoid the linear parking lot that will occur on freeways. Earthquakes just happen, with no real warning. And earthquake damage may be widespread, making evacuation difficult or impossible. In that case, it might be better to stay put.

If I decide to evacuate, how difficult might that be? The experience in Houston for Rita was instructive. What alternative routes are available? How likeley are they to be blocked by damage? If I try to evacuate but get stuck half way, am I in worse shape than had I stayed put?

What community resources are likely to be available? Some communities are much better prepared than others. In another thread, Lono talked about Red Cross shelters. Part of good planning would be to find out what is likely to be available (or not) in your area. If you live out in the country, there might be very few people around to help you. If you live in a big city, the authorities might be overwhelmed in a major emergency. Maybe you should get involved with CERT or other groups to make your community stronger?

Above all realize that things probably won't happen exactly as you expect. Plan for a variety of options. Don't get locked into only one plan. Being flexible is a good survival trait, in my opinion.