It looks strange to me that High-CPU Instances didn't come as clear winners in compilation tests. I thought of choosing only between c1.medium and c1.xlarge for

It looks strange to me that High-CPU Instances didn't come as clear winners in compilation tests. I thought of choosing only between c1.medium and c1.xlarge for my CPU-intensive tasks. Looks like I should look closely into all types of instances instead, except for micro and small. According to the specs Amazon gives us, "High-Memory" instances have 3.25 Compute Units per virtual core, while "High-CPU" only 2.5. It would be interesting to know what is going on: are their compilation tests unable to properly utilize many cores, or the nodes assigned to "High-Memory" instances tend to have more powerful hardware, or what?