The Duet with RepRapFirmware emulates Marlin, but not perfectly. Most people with the Duet use the web interface to control it, because it provides more information and control than any of the USB interface control programs. Several Ormerod users slice files with Simplify3D and then use the Upload & Print button on the web interface to save the gcode file to the SD card and print it.
Also, you get better prints if you print direct from SD card. The Duet USB interface is quite fast because there is no serial link involved, but even so, the data rate can't always keep up with the printer.
Also, you get better prints if you print direct from SD card. The Duet USB interface is quite fast because there is no serial link involved, but even so, the data rate can't always keep up with the printer.