Just throwing this out there, but Melanie has by far and long the weakest voice in the competition. Sure her tone is unique and cool, but she always goes quiet for the high notes and usually plays it pretty safe; paired with the fact she didn't get enough votes to get into the next live round and had to be saved by Adam, I have a feeling she won't be around too much longer.
For me, I think she's better just because her voice is so much different. The problem I've always had with the Voice is that they almost encourage oversinging, whereas Idol encourages undersinging. I like Trevin and think he has a great voice (I'm not gonna dispute that he won last night with that performance), but I think in terms of pushing boundaries and uniqueness, Melanie is a better choice. (The Trevin thing is in response to whoever mentioned it earlier, I can't figure out how Multi-quote works.)