They basically mean the same thing, that the company has stopped providing current financial information. The differnce is that "Delinquent SEC Reporting" applies to companies whose stock is registered with the SEC thus requiring them to file reports with the SEC. Most pink stocks are not registered with the SEC and follow the OTC alternate reporting standard. They get tagged with the "Dark or Defunct" label when they stop reporting.
Up until now, the SEC would typically only allow registered stock companies to go delinquent for 2 or 3 years before suspending and revoking their stocks while D or D stocks could keep trading for a much longer time before FINRA would eventually delete their symbol and remove them from trading. Now that the SEC has said they will crack down on D or D stocks, they both seem equally as bad.
p.s., I'm not an expert, this is just my understanding of how it works.
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