Comparison of Microsoft's sync tools to the cloud.

Below are a comparison (copy/pasted from the source) of the different Sync tools from Microsoft. It was updated on September 5, 2014. To be absolutely updated go to http://msdn.microsoft.com/en-us/library/azure/dn798669.aspx since things will change over time.

On-Premises to Cloud Synchronization

 

Feature	Azure Active Directory Synchronization Tool (DirSync)	Azure Active Directory Synchronization Services (AAD Sync)	Forefront Identity Manager 2010 R2 (FIM)
Connect to single on-premises AD forest	X	X	X
Connect to multiple on-premises AD forests		X	X
Connect to single on-premises LDAP directory (no AD at all)		CS	X
Connect to multiple on-premises LDAP directories		CS	X
Connect to on-premises AD and on-premises LDAP directories		CS	X
Connect to custom systems (i.e. SQL, Oracle, MySQL, etc.).		CS	X
Synchronize customer defined attributes (directory extensions)	CS	CS

Cloud to On-Premises Synchronization

Feature	Azure Active Directory Synchronization Tool (DirSync)	Azure Active Directory Synchronization Services (AAD Sync)	Forefront Identity Manager 2010 R2 (FIM)
Write-back of devices	X	CS
Attribute write back (for Exchange hybrid deployment )	X	X	X
Write-back of users, groups objects	CS	CS
Write-back of passwords (from SSPR and password change)	CS	CS
Write-back of customer defined attributes (directory extensions)	CS	CS

Authentication Feature Support

Feature	Azure Active Directory Synchronization Tool (DirSync)	Azure Active Directory Synchronization Services (AAD Sync)	Forefront Identity Manager 2010 R2 (FIM)
Password Hash Sync for single on-premises AD forest	X	CS
Password Hash Sync for multiple on-premises AD forests		CS
Federation (SSO)	X	X	X

Set-up and Installation

Feature	Azure Active Directory Synchronization Tool (DirSync)	Azure Active Directory Synchronization Services (AAD Sync)	Forefront Identity Manager 2010 R2 (FIM)
Supports installation on a Domain Controller	X	X
Supports installation using SQL Express	X	X
Step-up from DirSync to AADSync
Localization Windows Server languages)	X	CS
Support for Windows Server 2008 and Windows Server 2008 R2	X	X	X
Support for Windows Server 2012 and Windows Server 2012 R2	X	X

Filtering and Configuration

Feature	Azure Active Directory Synchronization Tool (DirSync)	Azure Active Directory Synchronization Services (AAD Sync)	Forefront Identity Manager 2010 R2 (FIM)
Filter on Domains and Organizational Units	X	X	X
Filter on attribute values on objects	X	X	X
Allow minimal set of attributes to be synchronized "MinSync"		X
Allow different service templates to be applied for attribute flows		X
Allow removing attributes from flowing from AD to AAD		X
Allow advanced customization for attribute flows		X	X