i only have a 60Gb HD and ive never come close to filling it.
it depends, do you plan to download ALOT of DLC (downloadable Content) and i do mean a TRUCK LOAD.
i dont but i DO install certain games to the HD, like BoP, Oblivion, and Op Flashpoint when i get it.
all in all, do you have the cash to spare, if so, treat yourself to the newer system, might have less overheat problems. but if ure on a budget that extra memory wont impact your life unless you're a massive DLC consumer whore
hehe