Should I choose 32 or 64 bit for Linux?

You should install 64-bit linux. Even though there are ways for the 32-bit kernel to address more than 4 GB the applications will still have a 3 GB limit.

"Here is one overview from LinuxForums.

I would hesitate if you do a lot of work with niche or developing tools written in entirely compiled languages. Many of the projects I'm interested in, like LDC, are only beginning to support 64 bit. Personally I'm holding off, but I'm holding off on more RAM too, so that's not an issue for me."

I run 64bit 9.04 for my home desktop. I do quite a lot with this machine, and the only 64bit related issue I encounter is stability problems with 64bit Adobe Flash.

Go for 64-bit. 32-bit can only access about 3.5 GB of RAM, and most of the compatibility issues have been ironed out. To make it even easier, use a popular distribution like Ubuntu.

To use all 8 GB naturally you should install 64-bit version.