Dipping will remove all of the paint, rust, seam sealer, undercoating,anything you dont remove from the car, the whole thing down to the metal. you will have to start over from square one, Even then, unless the shell is dipped into some sort of protective coating vat, the panels will be bare metal inside many places like the rockers and such. This will lead to corrosion every time the car is washed, and that is what you are trying to get rid of in the first place.
Media blasting isnt as invasive, but will strip all of the outside paint and bodywork as well. It usually leaves the seam sealer and other things that are harder to replace. Most of the pro shops seem to use Media blasting as their preferred method. If dipping is done, the car must be followed by the "E" coating to protect bare metal, as well as probably be dipped after the rust repair is complete to do a correct job. This is costly.