Dual motors:
1: The obvious one, MORE POWER!
2: More weight. Better traction.
3: Having that weight ON the axles, even BETTER traction due to lower center of gravity.
DIG:
1: Allows the rear axle to lock completely, so that when you turn the front wheels while on power the truck will pivot around the rear tires.
2: This lets you turn very sharply to get through tight spaces.
Worm Gear axles:
1: Awesome.
2: Smoother than standard gear driven axles.
3: Cannot be back-driven. (If you stop on a hill, and have no brakes, the truck wont roll back down.)
4: HIGHER gear redution ratio in a MUCH smaller package compared to standard gears.
I hope that answered some of your questions.
That Wreckluse tube chassis is pretty sweet!