the power consumption obviously lol this equals to lower heat production, and its most likely done because they make other cpus at that rating with similar performance. I know there are 140 watt x4 965 and a 125watt, along with 125 to 95watt, the lower watt cpus are released later in the series line and i would guess dont change in performance, but if any its not alot
Edit: the difference is one is a windsor series cpu and the other being an energy efficient brisbane cpu, the reason the wattage went down as the cpu went from the 90nm process to the 65nm process, seems the brisbane or 65watt cpu has less L2 cache only thing i can tell about the two just by specs