Do you believe you will be keeping the car for a long time? If so, for a car with rust history, the blasting will do nothing to stop the rust. Only replacing the entire panel or dipping will stop the rust.

When you get the car back from being dipped, you will be shocked at the extent of the rust damage.

Other than the cost, the biggest issue with dipping a car is re-sealing the seams and getting all the stripper out of the nooks and crannies. Left here it will continue to eat away at the metal. A good flush with a neutralizing agent is essential.

Blasting is only good for a car with minimum rust issues (past and present) or a car that is going to be flipped and the current owner is not particularly interested in the long term consequences.