Stu, I think the girl's video was recorded at home. And by emotion, I'm not talking about things like facial expressions and movement...I'm talking about the emotions that the playing elicits in the listener. She plays a lot of notes. He tells a story.
Jay, in my opinion and from my experience, the boy's playing is more technically and physically demanding.
The girl has great technique, but is essentially playing a lot of fast scales and arpeggios. Her left hand is doing a lot of repetitious movements in different locations on the neck. It's like drumming her fingers on a table, but doing it very accurately. Her right hand is primarily playing a steady stream of 1/32 (or 1/64) notes. It's fast, but not all that technically demanding. Also, she played with very little dynamics...her volume stayed at a constant level. But from the looks of
this interview, she's aware of the need to expand her "vocabulary" as well as her technique. Lastly, she's playing through electronic distortion and echo devices that "fatten up" her sound quite a bit. Not discounting her playing, though. What she's doing, she's doing very well, though. I doubt I could play that song these days, but I could pull off parts of it with just a little practice.
The boy is showing a wider range of skills with both hands, and some of the chord/melody positions his left hand is in are difficult (and get painful pretty quickly). His right hand is doing all sorts of techniques, and doing them all expertly. Also notice his dynamics...the soft parts and the loud parts. That helps add to the emotional impact of the music. And it's just him and the guitar. (And the traffic noises outside, LOL.) He's pulling good tone out of the guitar instead of relying on electronics to shape the tone. (And that's spoken by someone who likes to use the electronics a lot.) I had a semester of classical guitar in college, and it was some of the toughest guitar playing I've ever had to do. The instrument is physically harder to play than an electric guitar, and the traditional techniques (how you hold the guitar and how you position your hands) make it even harder. I'd have a much harder time playing parts of this song than the girl's song.
Of course, this is all just my subjective opinion. I'd be interested to hear the thoughts of other guitar players.