In essence the two versions are identical in terms of functionality, there are only some minor differences and it gives you a couple of more options, such as:
- LDAP/AD integration is possible in the installed/on-premise version
- You have full access to the database (MSSQL server or MySQL)
- You can configure the server yourself, for example specifying what SMTP server(s) that you want to use
- You can make minor changes to look and feel
- It is possible for you to extend the system in some areas by using extension hooks (good for integration with other systems)
- It is possible for you to extend the system by adding your own custom views
- And so on ...