Michael and Gabriel are more often associated with boy's names so I think Michael Gabriel just sounds rather masculine for a female name. Hunter Skye, I find to be rather nice. Although Hunter is more often used as a male name, I think Hunter Skye just has a nice, cute ring to it implying a strong female.
Although I'm not exactly a fan of either of these name choices for a girl, I do like Hunter Skye better out of the two. I don't really think Michael Gabriel flows that well; I think Mica Gabriel or Michelle Gabriella sounds better.
Sorry I meant to say Michael Gabriel for a boy but it wouldn't let me type it for some reason.