I prefer Melina, but Melia is ok. The sound of Melia lacks substance imo. It sounds like someone with a speech impediment trying to say Maria... but maybe I'm mispronouncing it. I'm not very good with Greek names. Melina is strong but feminine, would age well, and is uncommon. I only know one Melina. She's a very young 40 year old (you'd never guess she's 40), and a very cool person, and I really fell in love with her name. It clashes with our last name though, so I can't use it.
I've never heard Ionia, and I don't care for it. I do like Iona and prefer it to Ione.