Oh man, you pick a humdinger here. Love Johnny and love this movie. Here's my score:

Johnny & June = 98

Joaquin & Reese = 97

I also think Reese's voice tops June's (at least on this song), but Johnny makes up for it because he's Johnny. And no matter how amazing Joaquin was in the film (and he certainly was), there's no way I could put his version above the Man in Black's.