I have one of each ...
The MacBook is perfect if you just want to use it for browsing, email, and basic apps - photo editing/organizing, word processing, spreadsheets, etc.
The MacBook Pro is better if you need more graphics power, or are into video editing and other more taxing applications, and want a bigger display. The styles of the two are also different ... the MacBook Pro is bigger, but thinner, so not really much difference when hauling around.
The MacBook Pro is the only real option if you plan to do any gaming on it ... the 8600GT video card works great for games like Guild Wars, WoW, and the like. Both are capable of running Windows using BootCamp (or a third party app).
Also a good idea to see what happens this week, given there may be an announcements on either new versions of the existing notebooks -- possibly even a new version (rumors about an ultra portable) at MacWorld.