Hmm, it depends.
The aluminum macbooks use DDR3 memory, which is faster than the plain white macbook's DDR2 memory.  In my opinion, the DDR3 is a gimmick because you can only realize its power when it's matched with a Core i7 processor, which is not available in a laptop just yet.
I would bite the bullet on CPU speed and get the basic aluminum macbook (you won't notice a difference between 2.0 and 2.13 ghz (another gimmick if you ask me)).  I would upgrade to 4 gigs of ram right off the bat, because Mac users love to have a million things open, you won't notice slowdowns with that much ram.  The HD space is up to you, if you like to edit movies, have a lot of music/videos/pictures, I would consider the 250 GB hard drive.  With those options selected, you will have a nice machine that could take you through school and then some.
In the end you will have-
-Aluminium body for durability and style
-2.0ghz CPU, it will be enough to take care of your needs, especially when you compare it to the 'top-end' 2.2ghz CPU
-4gb ram, so you can have a ton of stuff running all at once
-250gb HDD, with obviously more storage than 160gb, but the bang-for-buck ratio would go down if you got the 320gb HDD
-Grand total