Mac Forum / General / Hardware / January 2007

Neither. Regardless of what model you get, both RAM slots will be filled.
You can't add more memory to a MacBook. You can only replace the RAM modules
that came with your MacBook with higher density modules. I use the plural as
modules should be replaced in pairs. If you want to upgrade from 1GB (which
means you have two 512MB modules) to 2GB, purchase two 1GB modules. You can
use single modules but it is not recommended. If you wish to know why, read
about the Intel chipset that Apple is now using.

If it's financially feasible, purchase your MacBook with 2GB of RAM. You'll
save money now and avoid hassles later. Besides, more memory is always a good
thing, especially in a notebook where increased disk access comes at the cost
of battery life.

I hope that helps.