Obviously the 64 bit if you want to make full use of the hardware capability of your system, but here are a few points to consider: What is in the 32-bit version of Office but is not included in the 64-bit version of Office? ActiveX controls library, ComCtl This library contains ActiveX controls that are used to build solutions. It is most commonly used in the following Microsoft Office programs: Access, Excel, and Word. SharePoint List control The list view in SharePoint Technology is not available to people using the 64-bit version of Office. This guy argues for 32 bit Office since the vast majority of users won't gain anything from 64 bit: The same things should apply for Office 2013 too.