quick thought on future proofing
It amuses me when others, and myself, argue on the boards over which particular model of a mac is more 'future-proof'. Nonetheless, I'm going to attempt it now anyway...
A few months ago, I was looking for a cheap, dependable mac portable to do some light lifting around the house and on the road: surfing, emails, word processing, and the like. I decided to go with a late model g4 12" laptop because of cost and form factor. My father had recently bought a 12" 1.07 ghz g4 ibook, and I was amazed by its usability for basic tasks, especially browsing on a decent wi-fi connection.
After looking, I eventually decided to scoop up a good deal on a last gen 12" powerbook with a 1.5 ghz g4 processor. Other contenders was a 1.33 ghz 12" powerbook and a contemporary ibook. My decision on the powerbook was NOT based upon the .17 ghz processor difference, but instead was based upon the feel and construction of the pb over the ibook, the slightly more capable video card of the pb (faster card and twice the video ram) and finally, the scrolling trackpad feature of the 1.5.
Based upon my experience, I would postulate that the differences in using a 2.0 whitebook, 2.0 uni mb and 2.4 uni mb three or four years from now would be a lot narrower. All three have the same video card, and the processor and ram differences between the three would arguably be minimal. By that time, I would expect apple to be releasing notebooks with four, eight or however many cored cpu's, and the software would hopefully be capable of using them all effectively. The .4 ghz difference would be negligible. I'm also discounting HD capacity since they're fairly cheap right now, and it is supremely easy to upgrade to a larger, faster drive on all of the macbooks.
The question becomes which features of the various notebooks would enhance its usability and desirability over time. The unis have LED backlit screens, which promise to have a longer useful shelf life over the whitebook; if the laptop is going to be your main machine and get a lot of constant use over the next 2-3 years this may be a factor. The unis also have the larger, arguably more useful trackpad. I have a sneaky suspicion that apple will start introducing features in its programs that will utilize the pinch and other features more over time. The unibodies have a, well, unibody design which promises to be more durable over time (I'll take a scratch over a crack in my case anyday). And finally, the 2.4 uni has the backlit keyboard, which is useful under low light conditions and has historically been a bit of a status symbol for portable mac totin' types.
I've got three sisters who are teachers. Granted, they're here in Oklahoma and you're in New York City, but based upon that I'm assuming that cash may be a consideration for you. Therefore, I suggest buying a refurbished model off of the apple online store, and I will base the prices accordingly. $850 for a modern whitebook, $1100 for a 2.0 uni and $1300 for a 2.4.
If the unibody design, LED backlit screen and trackpad are worth $250 (plus tax) to you right now, then get the 2.0 uni macbook. If not, stay with the whitebook. If the backlit keyboard is worth an additional $200 (plus tax) to you on top of that, then get the 2.4.
Or, you can prowl craigslist in your area and possibly find a last generation macbook pro, possibly with extended applecare on it, for roughly the same price. Good luck with your decision.