Copper heat sinks conduct upto 3x more than aluminum. The dissipation is about the same. The big reasons for built pcs to usually include aluminum is cost and need. Most systems dont need copper. Before arguing they do, because I always have a heat problem, its actually NOT the heatsink, but rather the fan. You also would need more airflow for copper, if used for its intended reason. You would use copper when there are HUGE amounts of heat (dual xeon, wildcat and oxygen type power house vidcards, etc), and then its not because of the disipation ratio, but due more because its maitaining ALOT more thermal heat then most normal heat sinks. So to let you know, copper is better in all aspects, but usually not needed, just a better fan is needed with more flow per cubic. Also, paste helps transfer the heat and provides a cooler solution for the sink to sit on instead of directly on the CPU. As far as the fins, they are there to increase total surface area. So, it comes down to cost and if its even necessary.