I'd be concerned about keeping an archive on either type of laptop. I've had harddrives go out on two of my laptop PCs and one of my PowerBook Pros. If you back up with a RAID (preferably wireless and automatically) then you'll be fine with either well selected laptop, IMHO. My Sony Viao is as expensive as a Powerbook but much better suited to audio, but either will serve your needs.
Dave
Dave