The functionality within Outlook is the same and there is also no (noticeable) performance increase by using the 64-bit edition. When it comes to Outlook, using the 64-bit version of Outlook does not have any direct benefits. The 64-bit version of Office also offers a security benefit as it always has Hardware Data Execution Prevention (DEP) enabled (although this can be enabled for the 32-bit version as well). Similarly, when you are working with large Word documents or PowerPoint presentations that are very rich with multimedia (pictures, videos, complex animations, etc…) or large tables or other embedded objects, the 64-bit version can be of help. Using the 64-bit version of Office will for instance allow you to work with large data sets like Excel workbooks or Project files that are over 2GB in size.

With the 32-bit version of Office, the application can only use up to 2GB of memory, even when more is available in your computer.

In general, the main benefit of using the 64-bit version of Office, is that it can use access memory when needed. I would recommend going with 64bit and reasons behind that as below:

Use ms office 32bit or 64bit?