It's also a question of which recording platform he's looking at.
If he's interested in Logic, the Mac is the only option.
Also, while Vaios may have more power in terms of hardware, OS X's audio and MIDI technology is so massively beyond what the rest of the industry is doing that it really isn't funny.
http://www.apple.com/macosx/features/audio/
And that stuff isn't just hype.
The MIDI implementation is just sensational.
The Core Audio stuff absolutely floored me when I first did nasty stuff like just unplugging my audio interface while playing music from iTunes, and CoreAudio dropped out for a fraction of a second before continuing on the internal speakers. It even automatically switched back to the external interface when I plugged it back in. It just works. (Though in how far this is supported for music production is still up to the authors of the audio software - even Apple's own Logic is still lagging in implementation of Core Audio's advanced multi-interface support, among many other things, but it's getting there in little steps...)
My USB (!) audio interface's driver defaulted to a latency of 2 milliseconds on a 400MHz G3 iMac under OS X. That is faster than most dedicated digital hardware mixers.
So, yeah...the Vaios have more power, but for audio, I wouldn't trade OS X for anything - at least with a view towards the future (read: G5 Powerbooks).
-s*