My order of cuteness is Nico, Hanayo, Rin, and all the rest are way down there compared to those three Goddesses of Cute, but Kotori is in the gray zone in between somewhere. Not quite on the same cloud as The Three but definitely cuter than the remaining five. Of course, the Paradox of Nico is that she's only cute when she's not trying to be.
I see Kotori as #1 in the Pretty faction, rather than cute per se. Nico is cute naturally and doesn't realize it, so tries too hard to be cute, thus obscuring her actual cuteness.
FWIW, I see Nozomi and Maki with her on the Pretty side, while Eli and Umi are on the Glamour side. Honoka is part Cute (in a Rin sort of way) and part her own unique thing.