In my opinion both have advantages and disadvantages.
For documents and reports that require expressions in the layout you need to use RDLC, because WORD has a static layout. For simple reports like lists you can use WORD. For example, dynamically showing or hiding sections, rows, columns, logo's is current not possible using the WORD layout.
RDLC imho will not be phased out, because of the fact that the WORD layout is too limited.
RDLC is perceived as complex, because it requires a steeper learning curve and Word seems easier. But in real life, in my experience the layouts are not really where the problem is, it's the dataset and how it's generated and sent to the layout(s). Because of the fact that it's a flat dataset that contains all, that you need to implement complex workarounds in RDLC and WORD. But that's another story ;-)
Also RDLC was developed by the SQL Server team and was never meant for Document reports. That's why it requires so many workarounds...
I think, Microsoft recommends WORD because it has a better performance rendering the layout. Personally I would recommend RDLC, and use WORD as a nice to have.
You also might want to have a look at alternatives, like Power BI for BI reports, export to Excel, and other third party tools, who are much more user friendly then RDLC and WORD.
This is my personal opinion. But I also know customers that are very happy using the WORD layouts.
It all comes down to what you know best.
