[Long Haired Git]

The only factor where aluminium is better is its weight, and so an aluminium HS can be bigger per KG than a copper one.

Think of this, Wing. Its the difference of temperature that makes energy (heat) flow. We NEED the energy to leave the CPU as otherwise it accumulates there as heat and the CPU boils and burns and the magic smoke escapes.
Now its true that a cold HSF would have a higher difference in temp to a warming CPU and hence more heat can flow.
The problem then is the heat is in the heatsink.
Now what?
If the heatsink doesn't get hotter, there will be no transfer to the air, as there is no difference in temperature to drive the energy flow.
So energy is coming in, and energy is not leaving, so it MUST get hotter (or make enough noise, or movement or other way to "bleed" the energy coming in).

So, as per incoherent, the specific heat which is how fast the heat sink will heat up, will be different. However, its the stable state we care about.

And that stable state is dependent on the design of the heatsink and how hot we can get it so there is a large difference between the heatsink and the air.

However, we want the CPU to be as cold as possible, and we don't want the heatsink to be hotter than the CPU otherwise energy will flow back into the CPU and heat that up.

So, its all about getting energy to flow from the CPU to air as efficiently as possible. Its about getting as much of the heatsink to be as near as possible to the CPU temperature so that the CPU is as cool as possible whilst still having a difference enough to bleed the energy to the air.

Oh sod it, I give up, there are the links above and plenty of other sites.

Now, I am assuming the followups mean you're serious, so here's a tip.
ProCooling is not a bunch of kids with PCs all out-ricing each other. Some of the posters here have many years working at companies full time on cooling computers. Most of us are in IT full time. Some of the posters above spend a bucket load of their spare time designing world class water blocks and helping improve radiator design. If you'd come in and said:
"I've done some research at these sites {link}, {link}, {link}, {link}, but I just don't get why copper is better than aluminium. Can I get someone to provide a good article or explain it to me?"
then you would have gotten a better response.
Instead, you came in and shot your mouth of about how you are right and everyone else in the world is wrong, you did it in CAPS and with crap spelling, and you're still arguing.

Despite this, people here are trying to help. Take advantage of this, and listen and read and ask good questions. Take the time to punctuate so we know you're trying, and we'll try too. That last post is better, but I'd like the next post to show you've read the links presented to you.

Now, on to you're last post. There is a way to keep the contact patch of the CPU at a constant temp, to keep it "cold". Its called a "peltier" or a TEC. Google that word and do some reading.