Rudy,
I am going to second Travis's suggestion that you look seriously at the 15" Macbook Pro. Macbooks are fine machines, and the ultimate balance between portability and usability, but you may find the display rather cramped. I recommend that you spend at least a little time on one at an Apple store before you decide.
The advantage to the 15" Macbook Pro is that it does have the discreet GPU, so you could use it for more graphically intense things, such as gaming. It will also benefit more from upcoming technologies in Snow Leopard, which will use the GPU for general computing purposes. In general, the Macbook Pro would cover more bases for you, given that you are not yet sure what field you might enter. Of course, it has a larger display, but it goes further than that. The pixel
density is also higher, meaning that each inch of display provides more Desktop space within which to work.
Maxing out the RAM on any machine you get is a good thing, but I will strongly recommend that you do not do this through Apple, but buy the RAM separately and install it yourself. This will save you some big bucks, which would allow you to purchase a better model of Macbook/Macbook Pro. We can and will point you to reputable places to buy the additional RAM. For instance,
here.
Again, there's nothing wrong with a Macbook, but I certainly wouldn't recommend it for anything graphic in nature, due to the smaller display and lower resolution. There's just not enough Desktop "real estate" to get anything serious done on these things, at least if it involves graphics. Don't take my word for it, because this is just my opinion. Do, however, go to an Apple store yourself and form your own opinion.
Scott