I have an Xbox 360 with a 120 GB hard drive. A big hard drive is important if you want to download a bunch of things (which I do), otherwise the 4 GB one is just fine. It never hurts to have extra space, though, IMO. As for Kinect, I haven’t seen any particularly good games for it (but a lot of bad ones). Until there’s some worth while game/reason for it, the Kinect is a waste of money. Just my opinion, though
yoga, dance games, physical training game are all good.