As per one of my other posts, I have the towing option, mainly because that was the easiest way of getting the towbar fitted for a bike carrier.
The option includes uprated brakes and cooling (of what, I am not entirely sure) so it is not simply a case of adding a tow bar. In Germany they are very strict about after market options, so this was the only way for me to go. It's a shame they don't offer it for the UK.