Between McPhee and Taylor, my vote goes to Taylor. He sings
well, he injects soul into his music, he manages to get the
audience groovin' to his songs week after week, and he's
consistent. He sings with a lot of heart.
McPhee has good vocals too but if you noticed, when she
overstretches it and goes for the high notes, she often falls
short. Also, she's over-dramatic and it's tired hearing her sing
all her songs with too much gusto! She's never sang songs
'tenderly' and certain songs you just NEED to sing it 'tenderly'.
She sings every song
like she's trying too hard to prove something... and haven't you
heard her missing notes, not really hitting them? 
We don't need YET ANOTHER Carrie Underwood or Kelly Clarkson!
Bleah! It's a formula
that's getting old. Chris Daughtry would have been a great American
Idol but siiiiiiigh, that's water under the bridge now, so my vote
goes to Taylor.