I recently posted a question and later found another similar question with an accepted answer. So I posted an answer to my question with a link to the other question. My answer was automatically turned into a comment due to its triviality. So the only option I have in order to avoid polluting SE with a question without a valid answer is to delete it. But that means that other users, who's searches would have otherwise been directed to my question, might keep on living their lives unenlightened about the issue. Or does SE store the deleted question and attaches keywords from my deleted question to the linked question or in any other way associate my question to the linked one?
If you delete your question, who is searching for a question using exclusively the terms used in your question's title would not find the related question (the duplicated question). If your question is closed, then who is looking for a question using the terms you used in your title would find your question, notice the question is duplicating another question, and read that question.
If I were you, I would vote to close your own question, and leave to the community the decision of deleting the question, if it is not really helpful (for SEO purposes) to leave your question closed. 20k users can immediately vote to delete a question, once it has been closed.