I don't know if it's the cosmic justice or anything, but according to Hinano, Megumi Nakajima was used as a character in Vocaloid (and presumably her voice was somehow used as a base for synthesized vocals there). I mentioned it just recently that Sheryl's singing was more dramatic and forceful in Macross Frontier than Ranka's, but since I listened to the OST without watching the same performances in original context, it was blatantly obvious that, in an surprise reversal, Nakajima is a better singer than May'n.

Hinano herself is ironically clueless about the selection:

I never really understood why they used newbie seiyuus as vocaloids.. The only feasible vocaloid I can think of is probably Gakupo since he is based off an actually GOOD singer. Otherwise they can grab any person off the street and be like “can you sing a couple notes?

Well, who never put her foot in mouth please throw the first stone.

The soundtracks and music by itself is essentially a different world, and Hinano may simply be not adept in it, have weird tastes and preconceptions, etc. Look how in another example of unexpected discovery, I've become a fan of Rie Kugimiya the singer after sampling her Iori in Idolmaster musical numbers off an accidentially purchased CD. And I thought she was only a two-bit seyuu for two-bit tsundere parts. Tsk, tsk. I'm no better than Hinano when pigeon-holing them.