The main difference is several hundred dollars. Seriously though, Google Docs(and others) lets you use Office type applications like Excel and Word online with most, if not all, of the functions. You can create and share docs with other people online so its especially good for collaborative work. As well if you want to access your docs from multiple computers without worrying about transferring them around Google Docs is a nice solution.
The main drawback is it requires an Internet connection so if you want to work on things when you are offline, such as on a plane, then that would be a problem. As well if you have a slow connection your user experience may not be as good as running Office locally.







