Should I switch to 64-bit kernel?

No.

 

I am going to soften that to a "probably not". But it does not cost much to try it, just boot with 6 and 4 held down and try. Reboot without that key combination to go back.

 

Well, any operation on numbers larger than 32 bits would benefit from a 64 bits kernel. Operations on numbers larger than 64 bits is twice as fast, and this is not only in theory, you'll notice. Applications dealing with media files for instance editing, encoding or decoding movies, or lots of operations in Creative Suite and audio programs would see a huge performance gain.

The guy answering a simple no to this question really has a lot to explain...

 

No, you are wrong on both points:

• Even the 32bit Intel processors in question have 64bit-wide integer and floating point units, and can use them in 32bit mode. So going to a 64bit kernel has not effect on this at all. The "bitness" of the processor and math units got uncoupled somewhere around 16-bit computing. It also was not "twice as fast", but many times as fast because of the way things had to come into and out of registers.
• Media file encoding does not see any improvement, since encoding goes linearly through a file. It can simplify things a little since you can map all of the file into virtual memory without having to create your own slices of the file, and do the management yourself. But this should not really speed thing up except from the development time perspective.

Now on Windows there is a large benefit from going to 64-bits because of the way they use the processor (for example the x64 AI allows for more registers). I don't know if MacOS X plays games and uses the extra registers or something, but it does not seem to get the same boost (or maybe suffer the same penalty in 32bit mode). But this is a completely different effect.

 

Right at the top of the forum:

http://forums.macrumors.com/showthread.php?t=783948