Al Williams on Medium discusses the steps to try out running Linux with a 64 bit kernel and the potential speed improvements.
Will it make a difference? That depends on what you are doing. Working with higher memory loads or USB 3 is probably going to be a bit faster. For some things, it won’t make much of a difference. Especially since all the applications are still running in 32-bit mode.
Just as a quick test, I tried to create a large file on the SD Card:dd if=/dev/zero of=~/test.dat bs=4096 count=512K
On average, the operation took about 104 seconds with the 32-bit kernel. With the 64-bit kernel it only took 76 seconds. That’s worthwhile, although depending on the task, you could see more or less improvement.
He cautions that not all software will run in a 64-bit environment and the very sensible advice to use a backup of the operating system in case of issues.
See the article here.