When it comes to Outlook, using the 64-bit version of Outlook does not have any direct benefits.The functionality within Outlook is the same and there is also no (noticeable) performance increase by using the 64-bit edition.
There also isn’t a 2GB file size limit for the 32-bit version of Outlook like there is for Excel and Project.
The file size limitation in Outlook is determined by whether you are using an ANSI or Unicode formatted pst-file.
Although the considerations for using 32-bit vs 64-bit are the same for Office 2010, 20, the default for new installations of these versions will remain 32-bit for now.
Luckily, it is easy enough to select which bit version you want to install in case you do not want the default one.
I seem to recall that Microsoft used to recommend to install the 32-bit version, even on a 64-bit version of Windows but that was some years ago.
As of the release of Office 2019, Microsoft is now recommending to install the 64-bit version of Office unless you have a specific need which still requires the 32-bit version.
In some cases the developer also needs to make some specific changes for 64-bit support or needs to wait for specific libraries, that the add-in relies on, to be recompiled for 64-bit.
Simply put; It’s a waiting game but nowadays most of the popular add-ins are available for both the 32-bit and 64-bit version of Office.
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.
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.
Similarly, when you are working with large Word documents or Power Point 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.