Which is better, copper or aluminum, for CPU heat sinks?

For CPU heat sinks, copper and aluminum have their own advantages, with copper conducting heat quickly and aluminum cooling down quickly. So the vast majority of heat sinks we see, including tower heat sinks, use a design of copper bottom and aluminum fins, which can maximize the heat dissipation efficiency of the CPU.
Of course, there are also pure copper heat sinks available, which are more common in rack mounted servers because they are very thin. If copper+aluminum is used, it will be limited by space, so they will simply occupy one end and use pure copper. However, there are many fans inside the server that are constantly blowing, and the air pressure of these fans is not low. If you have been to the computer room before, you will know that the roaring sound of the fan is giving you a headache.