OpenArena has a separate x86_64 binary and here the difference between the 32-bit and 64-bit installations come down to a 5% improvement for the Core 2 Duo notebook and 5% for the Core i7 notebook.
When it comes to running the Apache web-server in these different configurations, there is a 3% improvement when moving from the i686 to i686 PAE kernel and 2% on top of that when moving to the x86_64 Ubuntu. With the newer Core i7 Sandy Bridge notebook there is a 6% boost in performance with the PAE kernel, but the 64-bit performance strangely suffers a setback. In this test and the rest, they are built from source for the respective architecture.
When running the PostgreSQL server on the two systems, the performance is unchanged for the Core 2 Duo notebook with its 7200RPM SATA notebook hard drive. With the Core i7 notebook that has a high-end Intel SSD, there is a 15% improvement in performance over the i686 kernel regardless of PAE state.