I don't think being 'nice' is winning Scotty the vote
He's cornered the tween/teen vote (strangely, despite looking like the love child of George W Bush and Alfred E Neuman - but hey, what do I know about tween/teen tastes these days) plus he sings country, very authentically and that is a massive vote getter.
Compared to James and Casey - well Scotty has exactly the right type of voice to do exactly the type of music he's doing. Casey is a far better musician and is more musically talented, however I don't think his voice goes naturally where he wants it to go, it often sounds strained, forced and very affected.
Similar to James, much as he wants to sing rock/metal, his voice just doesn't naturally go there, he lacks power, his high notes are often screamed and there's very little distinctive about his vocals. James, again similar to Casey, does tend to go a bit OTT on performances, maybe a result of forcing his voice, he creeps into cheesey metal territory, whilst Casey creeps into 'I'm really glad I don't like next door to him, he's got a skeeery face when angry' territory
If I was voting, well I'd be voting for Haley, after her, no one really