Breadth of product line is not a very good differentiator for the same reasons price and quality aren’t good differentiators – they can all be copied by competitors. Even if you’re the first to establish a broad line, (i.e., a shampoo for every conceivable hair type and condition) other will not only follow but find additional types and conditions you hadn’t even thought of.
Now breadth of line is not a bad thing, it’s just not enough to differentiate one company from another, particularly in the age of “the long tail”. As more marketers concentrate on niches and serve specific market segments, breadth of line becomes irrelevant.
And actually, a better way to differentiate is to market exclusively to a particular market segment or two with products designed for their specific needs and desires, both physical and emotional.
That’s the way cult brands are built.