Little late, but my 2 cents...
I know this comes 5 months late, but anyhow I'd like to cast another vote for the MacBook (and please tell us: What did you got?)
And about the question: Why did I choose the MB over the MBP? Well it was ALMOST a no brainer, and I say almost because of the few amenities that the MB lacks and would be good to have: the backlit keyboard and cool aluminum enclosure, the nicer keyboard (I've had a powerbook, several iBooks and a MB, and no keyboard comes close to the PB's in comfort and pleasure for typing in) and the option to choose a matte screen (I am not really a fan of the glossy screen).
But, when it came to making a decision, did these three things justified spending about US$ 700 more?
I know the MBP offers more things besides the three that matter to me, but that's the point, they are things that doesn't matter to me.
I mean, I know it has a bigger screen (that's actually a disadvantage to me, as I really loved the small form factor of the 12'' PB/iB), it is half a pound heavier, and it has dedicated video memory, but those are things that I don't neither need nor want. So, once again, Was I willing to pay about 700 bucks more for a nicer keyboard and the looks of a computer? No way.
Just to be sure, I did a list of the things I would be doing on my computer: Web browsing/researching, taking notes, email, iTunes listening, PDF reading/annotating, Presentations, writing papers, managing my iPhoto library (work and personal stuff), managing a group calendar published to dotMac, video/text chatting to my family on another city, Skype to friends in other continent, spss number crunching, mantaining 2 websites (one personal, another work related), P2P sharing, OsiriX for viewing and exporting DICOMM images; and that pretty much was all. I realized that nothing of these required dedicated video memory, a bigger, more annoying screen nor a more expensive computer.
So, if your computer needs are something like mine, you won't get any benefit from expending another 700 bucks on a MBP. On the other hand, if you work constantly with video, or if you are a gamer, you'll definitely need to spend more on a MBP...
About what illicium wrote, it was taken care with the upgrading of the MBs to the santa rosa platform, a few months later:
"the MBP has a FAR better video card"
No argument here.
"Santa Rosa platform (800Mhz FSB..."
Same as the current MB, Santa Rosa, 800 MHz front side bus, however, the RAM is still 667 MHz...
"bigger screen"
An annoyance, IMHO
"...RAM capacity (4Gig max..."
Same as the current MacBook.
"...and more professional aluminum look"
I also like more the looks on the MBP, but then again, 700 for looks only. I'm not that pretentious (not yet)
