The difference between your XPS is the Black Macbook is that the guy was still using the macbook for daily tasks. Your XPS is probably on a shelf somewhere.
I guess my comment was a bit misleading in one way: I don't think Macbooks are necessarily a bad value or were a bad value circa 2006. But let me clarify:
1) My 2006 Dell XPS M1210 is my daily driver. It started life with XP and has exclusively run Ubuntu the last 3 years.
2) I had to replace the power adapter and disc drive under warranty, and upgraded from the original 80GB hard drive to a 500GB hard drive three or four years ago.
3) Otherwise, I can't remember replacing anything on it. The rubber feet on the bottom have fallen off and the left-click button on the trackpad is mushy. I'm convinced it's just some crumbs in the cracks, but I'm too lazy to fix it and have been content to just tap the touchpad to click.
4) I'm still using the original 9-cell battery it shipped with. The 6-cell I bought at the same time died, but the 9-cell is still barely usable, providing maybe 40 minutes' usage. Not great but not bad for 8 years old.
5) Again--I'm not trying to say that Macbooks are a bad buy, but my wife's 2007 15" Macbook has had far more expensive problems (to be fair, it's still with us too).