I have also read that these are essentially the same product and that the Collinite people actually said to go with the 476s. Supposedly the 915 has some extra perks in the form of scent and ? plus it's more money (also a bigger tin) but the products perform equally.
Do a search here or even call or e-mail Collinite directly and you can likely confirm this.
Their customer service is excellent and they are very honest.