The real answer is it depends on what you think what responsibilities exactly ESB or Workflow Orchestration should have. dragonwriter is of the reasonable opini

The real answer is it depends on what you think what responsibilities exactly ESB or Workflow Orchestration should have. dragonwriter is of the reasonable opinion that ESBs focus should be a message plane. If your of my opinion, ESBs generally include some of the features found in workflow. devonkim is also right in that ESBs in general let the business data/process bleed into the rest of the stack, where as with workflow, its completely agnostic to the business data/process. The most accurate answer would be from comparing various ESB products to Workflow Orchestration products, as every vendor/product will have slightly different opinions on where their responsibilities are.