Option A also keeps your logic out of the report, which turns the report into just a formatting tool.  This allows other tools, such as excel, to use the same source logic, which enhances reuse and makes reconciliation easier.  This will also allow you more easily to switch to a different tool if needed. 

Example: Crystal Enterprise is doing away with concurrent licensing starting in 2005, which will make the product much more expensive for some people.  Using option A would make it easier for you to switch to a new reporting engine such as microsoft reporting services.  I have heard rumors of someone creating a conversion tool to go from from crystal to reporting services.  This tool will probably work better if the reports are kept simple by keeping the logic in the sp's.