Well, the 2.4 comes with a 256 MB 8600 nVidia card, and a 160 HD. both the 2.2 and 2.4 come with 2 GBs of RAM now, so that's no longer a reason to get the higher of the two.
If you can, I'd wait a couple months for the refurbs to start coming along, and then grab a 2.4 for the price of a...