Difference between Serial Send and To Instrument

The Instrument Control Toolbox in MATLAB/Simulink contains two blocks that can send data to a device on a serial port:

    Serial Send: Send binary data over serial port
    To Instrument: Send simulation data to instrument

It looks like the To Instrument block is more general-purpose than Serial Send. To Instrument allows you to select the underlying interface, with one option being "Serial".

What is the difference between To Instrument (when configured with Interface=Serial) and Serial Send? Is there any reason to prefer either one for sending, say, 4 bytes of numeric data to the device? Are there any other situations where only one of them would work?