USB or Ethernet for controller interface?

Working on 32-bit microcontroller design that needs to interface to
industrial PC (mini-ITX, PC104, etc.) over short 3-meter cable. It is
an industrial application and the design will be DIN rail mounted
along side PLC's, relays, etc.

Any thoughts as to whether USB or Ethernet would be best?

Cost is a concern. Since this application's cable length requirement
is short, does this make USB the obvious winner?

Or, is Ethernet more robust in an industrial environment?

Sorry if this has been debated in the past. I did a search, but
didn't find much except for posts made in 2001. Let me know if there
are articles that address this.

Thank you!

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