The 7-Zip compression performance was close between the current Wheezy builds of Debian GNU/Linux and Debian GNU/Hurd with both having GCC 4.6.1. While close, the Debian GNU/Linux number was higher by about 4%.
When running CacheBench in a VM, the performance of both operating systems was nearly identical for the read and write speeds.
Debian GNU/Linux was slightly faster than Debian GNU/Hurd with C-Ray. Of course, each VM was only a single thread in this very parallelized benchmark due to the Hurd's lack of SMP support.