The advantage of 64bit when it comes to office and memory is really for handling very large datasets. But keep in mind that a very large dataset for Excel is a single spreadsheet file that is 2GB in size.
For compatibility issues with 32 bit plug-ins for Office, Microsoft recommends that you run a 32bit version of Microsoft Office. Almost all business environments continue to use the 32bit version of Office....and obviously business users have lots of simultaneous applications open all day long....and nearly all business users have 4GB of RAM or less.