When considering whether to use 32-bit or 64-bit Linux, you should consider the need and the usage of the system. If you have proprietary hardware, the drivers and software are usually written in 32-bit. You would also have less problem with software installation such as Adobe Flash player, Adobe Air and most media player, since most of them were written in 32-bit.
You could still install and use 32-bit software in a 64-bit operating environment. However, you need to download all the 32-bit libraries, wrapper and component for installation and compilation. This will increase your hard disk space since you need to maintain both 32-bit and 64-bit libraries.
You should consider using 64-bit operating system if you need to use a particular software application that requires speed and large amount of memory which is supported in 64-bit Linux. If you have more than 3GB of RAM, you should consider using 64-bit operating system because the 32-bit operating system only recognizes 3GB of RAM.
You could use some 32-bit Linux that addresses more than 3GB of RAM. Such Linux must supports PAE (Physical Addressing Extension), a feature provided by Intel.