No question I would stay with my V-10 Ford, just have had too good of an experience over the last 6 years and 50K+ miles to make a change. I tow a light cargo trailer, motorcycle and trailer only weigh 2,220# but especially if towing anything heavier the V-10 is the way to go. Not towing and have lots of money then the smaller Mercedes may be your cup of tea but...
Unless you drive hundreds of thousands of miles the fuel consumption differential will never equal the additional initial cost for a Mercedes diesel not to mention the increased cost of maintenance. No Mercedes C can even come close to matching the room and storage I have in our 24 footer.
As always... opinions and YMMV.
:C