From the OCZ Vertex solid-state drive, Red Hat Enterprise Linux 7 Beta 1 with XFS seemed slightly faster than Red Hat Enterprise Linux 6.5 with EXT4. Of course, if you desire, you can always switch to EXT4 when installing RHEL7.
Right away we're seeing some performance improvements in CPU-intensive benchmarks when upgrading from Red Hat Enterprise Linux 6.5 to Red Hat Enterprise Linux 7 Beta 1. Among the reason for this is moving from the RHEL6-modified Linux 2.6.32 kernel to on the Linux 3.10 kernel with the Intel P-State driver and various other enhancements. Also making a large difference is RHEL7 using the modern GCC 4.8.2 compiler by default in place of GCC 4.4.7.