If you work with Microsoft Office files on a regular basis and need 100% compatibility, SkyDrive might be the best choice due to its tight connection with the Office Web Apps. For Google Docs or OpenOffice users, however, either Google Drive or SkyDrive will fit the bill. Dropbox, of course, is just a storage, sharing, and sync platform — but you can still work with your files in the cloud thanks to support from web apps like Zoho.