[mikoto]

Assuming same design, copper is better.
This debate has been settled for years.

Some have said that copper conducts heat better while Alu "releases" it better. This is absolutely false.

In addition, galvanic corrosion IS a problem to consider, especially with components as small as we use. Corrosion inhibition is all fine and good but I would NEVER mix an Alu rad with a Storm block unless my coolant mixture was thick with corrosion inhibitors, and even then I'd always be nervous and forever checking the state of my equipment.

Consider also, the more corrosion inhibitors you use, the worse your coolant becomes. Water has excellent thermal properties, a very high (relatively) specific heat, meaning that per unit of water it can conduct a relatively large amount of thermal energy, and it isn't very viscuous at all. The more additives you introduce the higher the viscosity and the lower the specific heat, making for a slugish coolant. Not what you need for a Storm.

Water really is the best coolant out there. People have experimented with all sorts of ways to improve its thermal handling properties, the most successful imho is the Argon Laboratories solution of copper particles (measured in nanometers in size) suspended in water.

In short, the higher the proportion of water to additives in your loop, the better your coolant is. An aluminum radiator (less effecient than a copper one assuming the same design), necessitates the use of a higher volume of additives that will worsen the thermal characteristics of your coolant and probably not settle the issue of galvanic corrosion.

Consider this; is this man a computer water cooler or is he thinking from a standpoint of automotive use? With extremely hot coolant relative to air, and an extremely powerful fan + forced air from movement of auto + very high levels of anti freeze + no copper in the loop (only brass from heater core which is much less reactive). Which is better? The lighter, cheaper to manufacture aluminum radiator which no doubt performs great under those circumstances, or the heavier, more expensive, copper one? Of course this man sees no need for copper. What difference does 5-10C make in his world?