For whatever reason, I have never been much impressed by Inoue Marina's work. Maybe it's my imperfect Japanese.
HoTD doesn't change that, since I just hear surface angstiness and no emotional substance, myself. And until recently, Tsukiumi in
Sekirei has just sounded artificial to me. Now I begin to get the humor. And I do enjoy Marina in
Uragiri wa Boku no Namae wo Shitteiru.
I like her looks and personality. j1m0ne probably knows something I don't (she knows
a lot I don't), but Marina seems to me to continue to get plum roles, such as in
HotD. She's not headed for huge stardom, however, it appears, just for being a solid pro. And her intelligence and overall ability do make it possible that she will branch out into other areas. According to the lists in
Japanese Wikipedia, she is now getting even more game roles (no ero-games, it seems) than anime roles.
As for Omigawa Chiaki, she is one of the few amateurish-sounding seiyuus that really does give me trouble. I have trouble hearing past that flat voice. Although I am coming to enjoy her in
Seitokai Yakuindomo now.
To compare her sound with HanaKana or Noto Kawaii.... I haven't listened carefully to a lot of Omigawa-san's work, but I do think that HanaKana and Noto Kawaii can sound unlike their most popular voices (e.g., in
Darker than Black 2 and in
Mnemosyne, respectively). Whereas I have never heard Omigawa-san sound anything but flat. They definitely have far more professional voices than she does, with more life in them.