You Have to Go to That School. Applying for early admission isn't something you should do on every law school application. If you apply for early admission and you get in, you have to go. The decision is binding. So if you get into your third choice as an early applicant, and you later get accepted into your first choice law school, you're stuck. You have to go to the third choice.
Your Application Needs to be Ready Early. Because the application for early admissions is often due in October, you need to have your application done early. Not only do you need to complete your applications, have your essays done, and have your letters of recommendation in order, but you also have to be satisfied with your LSAT score. That means that if you're not happy with your October LSAT score, you may be forced to use it. If you apply for regular admission, you can wait for October's score, and possibly retake the LSAT in December if unhappy with your results.
You May Get No Financial Aid. By applying for early admission, you are signaling that you really want to go to that school. As a result, schools may not offer as many financial aid opportunities to you. Additionally, as the law school may be a reach for you (that's why you applied early), you may not be eligible for merit-based aid.
If you're thinking about early admission to law school, you should remember that this is not a decision made lightly. Think it through before diving into the application process.