When looking at the Apache web-server performance on the three systems between Ubuntu 11.04 and Fedora 15, Mark Shuttleworth's operating system always comes out ahead. It is not a small difference, but for the newest Intel Sandy Bridge system, it is a 44% advantage to Ubuntu 11.04 over Fedora 15.
On first glance, the compiler could be to blame with Fedora 15 using GCC 4.6 where as Ubuntu 11.04 is on GCC 4.5.2, while the kernel and other components are quite similar. However, past GCC 4.5 vs. 4.6 benchmarks at Phoronix have shown the Apache performance to be indifferent and certainly not to the magnitude of being +40% faster. This would be a huge GCC regression. However, other test results about to be shown, also highlight Ubuntu 11.04 as having faster disk performance than Fedora 15 even though both are on the Linux 2.6.38 kernel and an EXT4 file-system.
On the Sandy Bridge system with an Intel SSD, Ubuntu 11.04 was 10% faster than Fedora Lovelock in this database benchmark. On the other mobile systems, however, the PostgreSQL performance was slow and the transactions per second ended up being indifferent.
With PostMark, the Sandy Bridge system is 21% faster on Ubuntu 11.04 over Fedora 15 and 23% faster on Ubuntu for the ThinkPad T61 system. Only with the 32-bit Core Duo system was Fedora 15 slightly faster than Ubuntu 11.04.