I asked the same question, only in relation to the 1810 and 1810c - see my question and the Presonus response below:
"I am trying to understand difference between 1810 and 1810c . They appear to have identical specifications - only the color and the USB connector are different (I understand both operate at USB 2.0 speed - please correct me if I am wrong about that. Thanks very much. I will be using the interface with StudioOne Professional, naturally.
Colby Huval Today at 15:49 Hi Paul,
Thanks for contacting PreSonus!
You appear to already have the concept of the differences. The C version is basically an update to the previous silver version. BOTH are great choices. The C version just makes that leap into the C port becoming the standard connector being used and available now and in the future. Most modern computer are starting to include these ports so we decided it was time to refresh the line.
Please let me know if you have any further questions.
US Inside Sales