Since you have to write an essay on this topic, the first thing you need to do is some preliminary research. Fortunately, there is a good deal of information available about this topic, both in the library and on the internet. Also, if your school has any databases available, you should definitely check those. It would be helpful to know how long the essay has to be and how much detail is required. There are two basic ways to set up a comparison and contrast essay:
AAAAA / BBBBB
A/B A/B A/B A/B A/B
Once you've done your research and have decided which topics you'd like to focus on, we may be able to make some more specific suggestions. Remember that it's important to cite all your sources and to copy nothing. Students sometimes forget how greatly teachers dislike plagiarism and how easy it is to discover plagiarism these days. Sometimes students plagiarize without quite realizing that this is what they are doing; if you ever have any questions about what does and does not constitute plagiarism, never hesitate to ask your teacher.
Good luck with your research!