go pro if your goign to be playing xbox live. memory cards just wont cut it. it's definately worth it to just get the 60gb model. or, idk how cheap u can find a 20gb hard drive but get taht with an arcade if u want.
yeah you will undoubtedly eventually need a hard drive.
especially if your going online, theres lots of things that require hardrives.
if you think you will never use live the biggest memory card should do.
but if your even tempted by going online at all you will need a hardrive.
especially as MW2 will Surely get map packs soon after release, you cant fit map packs on Memory cards