120GB is good and all, but it is amazing how fast you fill that up. During my first year with my PS3, I filled up 100GB, just on game data, saved data (which takes up KB anyway) and a bit of music. Since then, I have upgraded it to 500GB, which is plenty.

Also, and this is where PS3 falls for me, is upgrading the HDD itself. Xbox is pretty easy, and much quicker than PS3. PS3 took me 6 hours to back up data, removed the HDD, then put data back on. Xbox, I understand, is a lot quicker, and easier as it is an unclip-replace kind of deal.

I think size is based on what you use the system for. If you are looking at playing a few games, bit of music etc, then 120GB is fine. But if you are like me and like to save EVERYTHING, then you are going to need a lot more than that.