My 15s fit nice in a mix. Though I only 4 mic the kit.I don't understand this, either. To fit into a mix, the least thing I'd like is the low-mid mud of large, dark hi-hats (and cymbals in general) that washes over electric guitars and strings.
And I also like the midrange "vocal"-ness of 14" hi-hats. Dark cymbals are gratifying on their own, but I find myself preferring brighter ones as soon as even my other drums start playing.
They also cut fine live, tighten up nicely for articulation, and slosh nicely when needed.