I'm interested in purchasing a Xbox 360, there are two different models I can purchase, the 250GB model and the 4GB model. I'm interested in getting into the hacking scene as I've always found that really fun, I've been Wii and DS hacking for a while now.
So I'm wondering, in terms of hacking, is there any difference between the two, other than the obvious?

NOTE: I will also be using this for the Media Centre Extender, is there any difference between the two?
NOTE2: I'm also in Australia if that makes any differences.