RDP connections support local device mapping, clipboard sharing, connection profile options (such as the ability to disable themes and wallpapers) and direct connections to the remote machine's console. RDP connections take advantage of the SmartScaling function built into the native RDP client. Active connections can be 'detached' from the main application window and reduced in size. The remote screen will simply zoom to fit - great if you are just watching a progress bar slowly moving across the screen on a remote computer. When complete, just click the 'dock' button to restore the session back into a tab and carry on as normal.
ICA connections support direct connections to servers but also to published resources. Universal Desktop Client can even query the Citrix environment over TCP or HTTP to enumerate applications available in the environment. Local drive mapping is subject to the same permissions checks as the native client. If the Citrix farm allows it, local printers will be mapped through, using the Universal Print Driver if so configured. Universal Desktop Client even allows for multiple concurrent connections to the same published resource, each with different credentials; something that's impossible using the Citrix Online Plug-in and time-consuming and awkward using the Citrix Web Interface. All stored credentials can be protected by a master password, entered when the applications starts. All stored passwords are encrypted using the master password, so if your workstation is stolen or compromised, Universal Desktop Client cannot be used to connect to remote computers using your credentials.