While Fedora 21 remains under heavy development, for some new benchmarks to get July started I ran some tests of a stock Fedora 20 installation versus Fedora 20 with all stable updates versus Fedora 21 in its "Rawhide" state.
These tests are just to look at the Fedora 20 updated performance and to offer a glimpse towards Fedora 21. Fedora 21 won't be released until at least October so take the results as you wish. Additionally, Fedora Rawhide tends to enable a lot of debug/development code that can potentially slow down the system compared to Fedora in its release form. Nevertheless, these latest Fedora Linux benchmarks should be interesting in their own right.
Fedora 20 with all stable updates at the time of testing (a week ago) included the Linux 3.14.8 kernel, GNOME Shell 3.10.4, X.Org Server 1.14.4, Mesa 10.1.5, and GCC 4.8.2. Fedora 21 Rawhide at the time of testing was loaded with the Linux 3.16-rc1 kernel, GNOME Shell 3.13.2, Mesa 10.2.1, and the GCC 4.9.0 compiler. The EXT4 file-system remains the default on Fedora.
All of this Fedora benchmarking was run in an open-source and easy-to-use manner via the Phoronix Test Suite.