Ideal Towing Vehicle?

Almost anything will tow that. The only exceptions I can think of are cars that cannot be fitted with a towbar at all like, I think, the Ka. You certainly don't need to be thinking along 4x4 lines for a dinghy. Things change for keelboats, especially larger ones, since all cars have a maximum specified towing weight for the braked trailers keelboats invariably use but 4x4s usually have a higher limit. I got my Subaru Forester in part because the max towing weight was comfortably above the 1000kg keelboat I owned at the time, whereas a lot of "family-type" 2 litre cars cannot legally tow a boat of that weight, once the trailer, mast etc are taken into account. 

I tow an F16, which at 8' 2" wide requires by a law a vehicle of at least 2 tons to tow it even though it weighs next to nothing. I guess when thinking of Mr Average sailor, I'm thinking 14' to 18' dinghy, probably an RS400 or similar?

mums mondeo estate 2 litre tdci (turbo diesel with common rail injection for non petrol heads) seems to be able to tow anything gets good fuel economy too.

my 1 litre polo tends to struggle a bit.

Ideal towing machine has to be a landrover defender