What would be the preferred way to store a query in SSRS or SQL SERVER?

Populate the data at report level is quite easy, but when it comes to performance, executing and storing the query in database level is always a best practice. SQL SERVER or any other database are specifically designed to store the data and execute the complex logic. They are optimized and have many specification/options to reduce the execution time of a query when it comes to large data. 

On other hand, SSRS is a visualization tool. It should be treated to show case the data only. The best way to normalize the situation is to use the parameterized stored procedure. Stored procedure saves the execution plan of the query in database and every time you run a query; execution will be optimized.  

It also depends on volume of data. So, I volume of data to visualize on the report is always less, then you can use table/views as well. Please try to avoid the queries with “SELECT * “.