What's so great about online courses?
Online courses have made it easier for people to work full-time and go to school. An online class usually allows you to do your coursework when you have time, so you aren't stuck trying to figure out how to make your work schedule mesh with your school schedule. Online courses also allow you to take almost any classes you want, because you aren't restricted to the schools in your geographic area.
What's the downside?
While online courses allow maximum flexibility, they can eliminate most person-to-person contact. Most of your communication with your professor and fellow students will be online, through email and live chats. You'll miss out on the dynamics of learning in a classroom and interacting live with other people.
What's the benefit of going to college the traditional way?
The "real life" college experience is about much more than traditional classroom learning. For young adults, college can involve living independently for the first time, meeting new people, and learning to manage your schedule while making choices on your own. Real life college also offers numerous clubs, sports, social events, and community service activities that online courses can't provide.