The Bitsource only compared the compile time of a Linux kernal, but according to this article, CloudServers > EC2 (better performing, lower cost).
Here’s what the article is about:
“The Bitsource conducted a review of the two cloud computing platforms, Rackspace Cloud Servers and Amazon Elastic Compute Cloud (EC2), to get a general idea of overall system performance. Included in the tests were pure computing power (CPU), and raw disk I/O throughput. Using a consistent testing methodology across most instance sizes over a two-month time span (a painstaking process requiring lots of patience) has resulted in the following comparison of CPU performance, disk performance and cost between the two platforms.”