Should I ship my car or buy a new one after moving?

Moving across the country is already a huge headache, and then you have to figure out what to do with your car. Should I pay to ship my old, paid-off car, or is it better to just sell it and deal with buying a new one in a new state? There are so many factors, from shipping costs and taxes to new registration rules, and it's tough to know the most economical or practical choice.