32 bit Office will run fine on a 64 bit OS. The reason that Microsoft recommends running 32 bit version for most users is due to compatibility with Office add-ins and other applications. Moreover, when you install 64 bit version a 32 bit version is installed as well.
There are advantages to x64, but they aren't commonly utilized. One big difference is a 2GB file size limit that set on the 32 bit apps.