Most high school students get a job or an internship for over the summer(or all year long). I chose the route of an internship instead of a paid job at a fast food place- or something of the equivalent- because the career oriented experience was worth more to me than money. Colleges and future employers like to see that you have had some sort of job experience. In my opinion, internships have more benefits than normal jobs.
By doing an internship or a shadow program you get to go through the motions of the career you hope to later have. Doing this type of experience can also really help you narrow down career path options. Doing an internship you can find out what things you really like to do and what things you do not really like to do. As many people change majors in college because they learn more about what they are really interested in, high school students in internship programs can figure out their career preferences much earlier and hopefully avoid changing majors in college. You can also benefit if you know you want to go into a broad field such as medicine or engineering, but you do not know what specialty you want to go into. This summer I learned a lot about what specialties in medicine interested me and what specialties were not as good a fit for me as I thought. Overall, internships and shadow programs give you inside experience that you could not get elsewhere before entering college or graduate school.
Internships also give you an edge when applying for jobs down the road. All employers want employees who have experience doing some sort of job or internship. This shows that the people have experience being on a schedule and being held responsible. Someone who has an internship experience relevant to the job being applied for will have an edge over someone who worked at a Jamba Juice or Culver's. The relevant experience you can get at an internship cannot be matched at a normal job.
On the other hand, I understand the need for money from a regular summer job. For someone paying their own way in college or someone who knows they will not receive very much scholarship money at their choice college just getting money from any place may be a priority. I understand that money issues cannot be easily fixed with simply working a job, but if there is a way to do an internship or other relevant to your career task you should always try to jump on the opportunity. People will always be impressed with you for having career relevant experiences. For all these reasons, internships are better than regular summer jobs.