Fourtrak or Moretrak?

Starting out as a competition between different traction vehicles I now am immersed in a big debate - which would better pull a trailer from a muddy field - a naturally habitant, lightweight (in comparison) secondhand daihatsu fourtrak or a more modern but a lot more heavy duty mercedes sprinter van. Now you would think that the 4x4 would wipe the floor with a big old german white van but it didn't when we tested it - I was gobsmacked - how is a huge van with poor tyres (grip depth wise compared to the 4x4) beating a 4x4 in the towing challenge - surely thats not really a possibility. Perhaps the germans have done it with clever traction control...more testing I think.