As fast as your slowest piece...

We all know that our laptops and desktops are only as fast our our slowest piece. So I've decided to go with the Macbook Pro and trying to decide what guts to put inside it. So my questions are which is faster, the 1GB (2x512ram @ $100) or the 1GB (1 S0 DIMMs @ $200)? And if I were to get the faster one of the two, what would do it more justice, 120GB @5400rpm $200, or the 100GB @7200rpm $200? Any help you can provide me would be greatly appreciated. Thanks.

If you are going to be using this as a desktop replacement system get the 1gb I was told by somebody at the apple store that it is faster to have one stick pluss you can upgrade later, but if you want good battery power I would say go 512x2 since i heard that is better on batter, again I don't know how accurate that is.
again desktop replacement get the 7200rpm drive its faster and not as good on battery so if you are going to be using it more as a portable system then get th 5400rpm drive.