A reputable blaster can help you decide based on the condition of the machine. Many times they need to do both to get the job done right.
I always have them start with a bead blast first to remove the paint, sealant and decals so you can see what you have to work with. Then, if any rust areas are found, I have them sandblast that area only.
In then end, if you get it down to solid, clean metal and you don't warp anything, it doesn't matter how you did it.