Today Office 2013 was RTM’d (Released to Manufacturing) and again the question of 32bit or 64bit has come up. Microsoft’s answer is also my answer:
In most cases, install the 32-bit version of Microsoft Office. We recommend the 32-bit version of Office, because it helps prevent compatibility issues with most other applications, especially third-party add-ins.
Office installs the 32-bit version automatically even if your computer is running 64-bit editions of Windows. You might want to install the 64-bit version of Office if you usually work with extra-large databases or worksheets
The only real improvement on 64bit Office 2013 is performance on VERY large spreadsheets.
The only real drawback on 64 Bit Office 2013 is that most add-in’s are 32bit and as such will not function. Most people do not use Office add-ins so you likely will not notice it… but you might, so stick with 32bit for another few years.
Read this short Microsoft article for more details