Advantages of using sodium percarbonate

• It is a granulated powder – which can be nice for scrubbing stains and stuck-on-gunk off of dishes. Think of scouring powder, but made out of hydrogen peroxide. It can be made into a paste, too, and used on tile grout and tough stains.
• Sodium percarbonate is easy to carry around -- say, to a laundromat – because of its dry powder form. In fact, laundry products are one of the big applications of sodium percarbonate.
• It’s cheap. Really cheap: a few dollars for a little tub of it. The recommended amounts are small, it is very concentrated.
• It is easier to ship than 35% peroxide, since it is not a “hazardous material” for shipping purposes, at least in small quantities. (This is confusing – I’ve seen at least one source that does ship larger quantities, over a couple of pounds, as a hazardous material. I’m not convinced that this is a general practice. I thinkSodium percarbonate is generally shipped as usual, not as a hazardous material. I'm thinking that "pure" sodium percarbonate requires hazardous materials shipping. I'll update this when I know for sure what the distinction is.)
• It is less likely to splash and spill than liquid peroxide, so it is safer to work with. One does still need to be careful with it, but mostly once it is mixed into water.