For towing with a gas engine I would get the 4.10 (which is the lower gearing). If you get a diesel your only option will be the 3.73 which will do just fine.
Please don't judge a diesel engine by a 1984 Mercedes. Try comparing anything else from 1984 to today's technology: computers, cell phones, televisions, etc.
Diesel engines have come a long long way. Unfortunately a lot of Americans still seem to make those comparisons to long past diesel technology. I think that's why we don't have as many diesel vehicle options in this country.