Several advantages. Soda blasting will remove material all be it a very small amount. Vapor blasting doesn't. Vapor blasting actually peens the material and makes the material stronger and more resistant to corrosion. Vapor blasting also deep cleans the material via the hydrostatic shock of the glass beads impact on the material in a wet environment. The dust from soda blasting is pretty caustic for lungs and any plants near by. Vaporblasting isn't. Soda blasting is a 1 shot deal. Once the soda is used, is used up. Glass beads can be reused.
-P.