I was referring the Alu MB with the 9400 (not the whitebook) and the low-end MBP.
If you do a direct comparison, they are almost identical in performance features. Same processor, same fronside bus, same L2 cache, same RAM, same stated battery life (MB is better), same backlit keyboard, same trackpad/design, same HD... hell, the only difference is the 9600... and even then, I'm not sold. The only foreseeable difference would be gaming, but even then, there is no guarantee that there will be substantial improvement. After all, the MB can still play COD4 and what not. By the time the 9400 video card is outdated, so too will be the 9600 (it's really not that great compared to other offerings right now anyway).
It sounds like someone doesn't want to face the facts... all your extra money bought you was a better screen, a slightly better video card, and a bigger, heavier frame (with less battery life). If you think that's worth it, then good for you.
And there's no comparison between a $500 Dell and a MB. I bought the computer for various reasons, not just hardware configuration (e.g. OS, build quality, design, resale value, etc.).