syntaxHighlighter plugin

[hameau]

what is the difference between a general plugin and the editor-implementation
what are the pro and cons ?

It's up to the user to decide what the pros and cons are for a given plugin. I don't see that the plugin author has to justify his work at all, beyond "This scratched my itch, this is what it does, you may find it useful, too."

Does it duplicate a similar feature for CKEditor? Quite probably, from a front-end visitor view. So what? It's a different way to get the same result – choice.

If I ware arrogant, I would not contribute in a forum at all, I would keep my knowledge (and questions) for me and share nothing with others.

I'm afraid what you write often appears to be arrogant, though I am sure it is not intended that way.