DropBox
Dropbox offers 2GB free space for its users which is low as compared to other services. It also has great referral programs in which users get 500MB and you also get the 16GB for referring people.Dropbox includes high prices .Drop box sync is a robust web app and allows you to drag and drop files for uploading .Backup is one of my favorite as it has a very good repository and keeps the thirty days back saved files .Another feature of the Dropbox that is really nice is that it makes easy sharing of files.
Google Drive
It offers free space of 5GB which is a step ahead from Dropbox. It is much cheaper than other services Google drive offers apps for Android, Windows, and Mac. Similar to that of Dropbox storage services Google drive also keeps backup of files for thirty days .It also offers its users to save a revised version of files which can be saved forever. It only offers shared with other users having a Google drive account.
Microsoft Skydrive
Users get 25GB free space. Microsoft skydrive offers three plans for pricing. This is the only service that can advertise Windows phone integration. It offers an iOS app but has no Blackberry and androids and has Mac and Windows. It requires a 64bit machine for Windows. It keeps records of the files for thirty days. It offers shared in a great manner and users are provided with a link and users can even edit their documents. It also includes Twitter buttons and Facebook.
Apple i Cloud
Appleicloud offers a free space of 5GB the price is better than Dropbox. In sync this is different as compared to other services. Users cannot browse files individually but there is no file system. Users can view their files from online iWork.On your computer you will need a Windows Vista or Windows 7and Mac OSX lion .It does not offer any backup services.
Amazon Cloud Drive
Amazon offers 5 GB free space and unlimited storage space for music. The price is reasonable and unfortunately Amazon cloud drive fails in sync. There is no sync ability as it has a web based interface. You will not find any versioning with cloud drive and there is no sharing either.
Box
It offers free space of 5GB and you can even expand it by signing up with advertisements. Box has several types of pricing accounts Enterprise,Personal and business.Box offers for personal accounts iOS and androids and has no desktop version app. You can upgrade it by paying for the account to get your desktop sync. Backups are available for only those users those are having premium accounts. It offers easy sharing .Users can work with others on sharing files but depending upon the plan they are having.