<p>When do we use client side reporting and when do we use server side reporting?</p>

<p>Which reporting is best practice (client/server)?</p>

<p>This pertains to SSRS reporting.</p>

Well... client side reporting you'd use if you've got something like a winforms client that you can't guarantee will have constant access to the data source. It might have a set of data cached on the client side which you need to report on even if the connection to the server is unavailable.
Server side reporting you'd use in the scenario where you either need to simplify the report distribution and deployment as you just deploy the reports to one place and everyone can access them. This has the downfall of always requiring a connection be available to the server