No change in the OpenSSL performance between either the 32-bit kernels, but the 64-bit kernel on the Intel Core 2 Duo "Penryn" was approaching two and a half times the speed of the 32-bit kernel.
With video processing using x264, the PAE kernel performance just dropped ever so slightly while the 64-bit kernel was again the fastest option.
Only a very small drop in performance can be found with the PAE kernel in the PostMark disk test, but the 64-bit kernel was immensely faster.
In the fourteen tests for this article we did not find using Ubuntu's 32-bit PAE kernel to have a dramatic performance impact whether it be positive or negative. Granted, we were using just 4GB of system memory that is common to many desktops, but if using 8GB, 16GB, or even a greater memory capacity the performance penalties are perhaps higher. By far though exhibiting the best performance was the Ubuntu 64-bit kernel that often ended up being leaps and bounds better than the 32-bit kernel. Unless you have technical or business reasons for not migrating to 64-bit Linux with compatible hardware, there is no reason to stick around with a 32-bit kernel and worrying about physical address extension. If you want to run your own kernel benchmarks, give the Phoronix Test Suite a try that offers more than 120 test profiles and 60 test suites.