well it depends if you need the capacity also. I'm looking for the 200gb Hitachi for my Macbook too; I have the 2Ghz white one so only have 80gb, which isn't enough. Also I tend to do quite a lot of writing and reading to/from the disk in the form of large file transfers and writing to MySQL databases. With my Macbook hooked up to a 22" LCD and a mouse/keyboard I effectively use it as a desktop replacement (not a gamer), so it makes sense to get the fastest and largest HDD available.
Unfortunately I got my Macbook just before the latest update so it doesn't support 4gb RAM, but 2gb seems pretty smooth to me (even with Leopard).