You have to careful comparing one specific EC2 instance with other providers. Unlike most compute services, EC2 infrastructure is heterogenous. The c1.xlarge instance compared might deploy to 2 or 3 different chipsets in us-east-1, each with different performance characteristics. Based on the results they posted, this instance appears to have deployed to a 2.13GHz E5506 host. Most likely, Brightbox is using a homogenous infrastructure, and likely something a bit faster, like X55, X56 or E5s. For a more apples to apples comparison, they might have tested against an m2.4xlarge (8 cores) or cc1.4xlarge (8 cores hyperthreaded to 16), which are also 8 cores and deploy to X5550, X5570 or E5-2665. Based on my own benchmarking either of these instances would have performed comparably or better than the Brightbox 8GB instance.

The point is, you have a lot of options with EC2 in terms of performance, and comparing a single instance deployment doesn't really do it justice.

[Edit] Here are a few links to Phoronix results for EC2 instance types not included in their testing. m2s, cc1s and cc2s are the better CPU performers in EC2 due to faster processors. If you do a CPU performance comparison, these instance types should not be excluded (as I observe they often are):

m2.4xlarge - 8 cores - X5550 http://openbenchmarking.org/result/1208019-SU-CLOUDHARM39

m2.4xlarge - 8 cores - E5-2665 http://openbenchmarking.org/result/1208139-SU-CLOUDHARM43

cc1.4xlarge - 8 cores/16 HT - X5570 http://openbenchmarking.org/result/1208127-SU-CLOUDHARM93

c1.xlarge - 8 cores - E5506 http://openbenchmarking.org/result/1208134-SU-CLOUDHARM15

These instances were tested using CentOS 6, which will be a bit slower than Ubuntu 12.04.