So I will not get into ALL the advantages of Windows 7 over Vista, but I have recently been hired to review and repair laptops running Windows Vista. There are endless scenarios where the machine becomes unresponsive. Not just older Vista machines, but newer installations, and fully updated installations as well. From my take on reading and experience trying to repair them, I would say that this was moreso an experiment and not a worthy release product. There is endless drive churning and pointless freezing on ALL of these machines. The same machine, with a fresh Windows 7 installation, runs smoother and much more reliable.
Of course it needs to be said that these operating systems require at least 4GB of RAM (memory), a multi-core chip from AMD or Intel, and a graphics card that gives you at LEAST 128MB of video memory, if not 512MB.