main difference appears to be the President can fire a special counsel, not a special prosecutor.
Here’s what I had found that was half way decent.
http://www.pbs.org/newshour/updates/special-prosecutor-democrats-want-no-longer-exists/
Thanks for that article.
Here’s a key paragraph: “There are Department of Justice regulations for preserving autonomy, but none of that prevents the special counsel from being fired by Trump for any reason whatsoever, Persily said.”