The 5 unique features of Parallels that I found on their site:

The following Must-Have features are only available from Parallels:

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SmartSelect
Let your applications break free from their OS prisons! Set any Windows or Mac application top be the default for any file from either OS.
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Snapshot Manager
Save the state of your VM’s memory, settings, and hard drive with a single click. Create and manage as many snapshots as you want, and revert to any snapshot at any time.
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Parallels Complete Shared Folders
Share files between OS X and Windows with easy-to-setup shared folders and “drag-and-drop”. Mount the Windows drive to the Mac desktop for instant access to Windows files!
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Parallels Explorer
Access your VM’s files and folders straight from the Mac desktop, even if your virtual machine is shut down.
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Kaspersky Internet Security
Protect your Windows virtual machine from viruses and spyware with a FREE 6-month subscription.