real4u2c,
Do you already have a vehicle which can be safely towed four down? If you have to buy another car either way, than one option might be better than the other. If you already have a car which CAN be flat-towed, or have one that can't be dolly towed, or one that can be dolley towed...well....you get the idea.
We have always flat-towed and I think that's the most convenient way. But, it's usually the most expensive, as well. Our car (2001 Honda Odyssey) doesn't require any special equipment to be flat-towed.
So, first question: what type of vehicle do you have, or are you buying another?
One other thing, your Workhorse chassis is probably the W-22, correct? Or is it the W-24? If it's the W-22, the towing limit is the lower of the hitch rating (probably 5,0000 lbs.) or the difference between the GCWR (26,000 lbs.) and the weight of the rig as your travel down the road. The GVWR of the W-22 is rated at 22,000 lbs. so if you weigh in about 22k, your two rating is only 4,000 lbs. (26,000-22,000). So another suggestion is to have your rig weighed fully loaded as you travel.
One last things, the owner's manual of your chassis states that an auxiliary braking system is necessary for towing most vehicles. Many people ignore that, my recommendation is to follow that statement.
~Rick