I prefer the Freedom Harness over the EasyWalk because it is generally more secure (I've never had a dog slip out of the Freedom Harness, but I've had a couple get loose from the EasyWalk). That said, I've used both with good success for my fearful dog Pongu, who also used to bolt in terror from trucks/people/plastic bags/everything on earth.
I would not use a prong or other aversive device for a fearful dog. It's just going to make things worse by adding pain to the terror that the dog is already experiencing, which is the complete opposite of what you should be trying to accomplish.
ARCHMX TDCH Pongu the Insane, CD-C, RE, RL1X6, RL2X5, RL3X2 (GSD mix, b. Apr 2010)
Crookytail the Tigerwuff, RL1, ITD (Akita mix, b. Jan 2011)