Ubuntu 14.10 Linux 32-bit vs. 64-bit Performance
With the disk benchmarks there can be some performance improvements depending upon the particular disk workload. These results aren't very different from the past...
With some common open-source games that are 64-bit capable, there wasn't anything major to gain out of the 64-bit Ubuntu 14.10 release. Hence why most Steam on Linux games aren't too concerned about 64-bit Linux builds, besides potential compatibility issues.