Every year or two we run >32-bit vs. 64-bit Linux benchmarks. While x86_64 Intel/AMD hardware has been extremely common for quite some time, we continue to be amazed at the number of people still running an i686 Linux distribution on x86_64 hardware.
At least in the past year or two we've seen most Linux distributions finally endorse their x86_64 ISOs as their preferred installation media over i686. Some distributions have also worked to demote their i686 spins and some have stopped producing 32-bit x86 install media entirely. Fortunately, there's also been little reason these days for x86_64 hardware owners to consider using a 32-bit Linux distribution with Adobe Flash, Java, Linux gaming, and other past challenges having been settled in a 64-bit Linux world. About the only logical reason left for some x86_64 owners to still use 32-bit Linux is if you have less than 2GB of system memory, but even then for those older systems currently at 2GB of less of RAM, DDR2/DDR3 is incredibly cheap these days.
Anyhow, as people still seem interested in the 32-bit vs. 64-bit Linux distribution benchmarks, here are some tests I did on an ASUS Zenbook. The ASUS UX301LAA was equipped with an Intel Core i7 4558U Haswell CPU with Iris Graphics, 8GB of RAM, and dual 128GB SanDisk SSDs. Ubuntu 16.04 daily development snapshots from the same day were used for comparing the x86 and x86_64 performance on this system with the Linux 4.4.0-11-generic kernel, Unity 7.4, Mesa 11.2, and GCC 5.3.1.
All of these benchmarks were done in a fully-automated manner using the open-source Phoronix Test Suite software.