WARNING: The CoRD/rdesktop plugin is NOT supported anymore in Royal TSX 2.0 and higher!
The FreeRDP based plugin is preferred over the CoRD/rdesktop one.
FreeRDP offers a lot more features than rdesktop, including support for NLA and TSG in the future.
Also, I have already stopped updating the CoRD based plugin with new features. The only updates you'll get for it are bugfixes. And eventually I'll probably phase it out altogether.
The only reason the CoRD plugin still exists is because it provides a fallback in case the FreeRDP plugin has trouble with a specific host. Because I can't test every possible configuration and emulate any environment in existence, I opted for not instantly removing it from the list of available RDP plugins.
Bottom line is, use the FreeRDP plugin. If you have any trouble with it, please report them to me and only if I can't figure out what's going on, the CoRD plugin may provide a solution until that specific bug gets fixed.