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Blinn is very close to Phong, but with a slight difference. For back-lit highlights, where the light is nearly behind the object and is still casting a highlight on the surface, Phong tends to spread that highlight out across the surface. while Blinn keeps it the same size as it would with the light in front of the surface. The highlight remains round, rather than spreading out. Other than that, they're virtually identical. In use, I would use Phong for surfaces that are supposed to be a bit drier or worn. The spreading of the highlight at these angles lends a bit of a dusty look to the surface, where Blinn gives it a cleaner, freshly polished, or even wet look.