I personally have had both a detachable swan neck and now a fixed towbar on my a6. Detachable was changed after a rear end shunt.
To be honest it never ended up being detached but both the swan neck and fixed have both coped towing race car trailers without issues. Swan neck is obviously less likely to affect parking sensors and is nicer looking. On a fixed one you can't remove the tow ball, or you couldn't on the one I had. Think it was a witter one. Here is a review of all main types of towbars which might be useful:
https://autoevoke.com/index.php?/forums/topic/8998-types-of-tow-bars/
Cheers
Steve