The CPU benchmarks comparing Fedora 19 and Fedora 20 weren't interesting at all since both versions of Fedora are using the GCC 4.8 compiler by default. Fedora 21 should bring some changes as it will likely ship with GCC 4.9.
Overall, between Fedora 19 and Fedora 20 the most pressing end-user performance changes would certainly come down to the open-source graphics drivers that are constantly being improved try to reach parity with the proprietary Linux graphics drivers. Sadly, there isn't Mesa 10.0 in Fedora 20 that would have brought even more performance enhancements, but at least by upgrading to Linux 3.12 on Fedora 20 you might see some extra gains.
Feel free to benchmark your Fedora Linux installation using the open-source Phoronix Test Suite software. Coming up next week will be some new Ubuntu vs. Fedora performance numbers.