Tulip2,
You mention 4 somewhat different products. My first questions would be along the lines of your project requirements - amount of data, types of reports, reporting functionality, local or distributed users, security concerns, usability, etc.. After that you could probably easily filter out several BI vendors. For example, MicroStrategy is known for handling very large datasets many users. Business Objects is know for handling small to medium size datasets, but it's architecture breaks down when you try and support too much data and too many users. Brio is more a desktop OLAP product, where a small dataset is downloaded to the client for analysis (see ROLAP/MOLAP/DOLAP discussions in the Data Warehousing General Discussion group). Crystal is a very good report writer, but not known for large datasets or ad-hoc capability.
Some other vendors you may consider include Siebel Analytics, Hyperion Solutions, Cognos, and Actuate.
Finally, if you aren't working directly with the vendors yet, a lot of them have direct comparisons on their websites, such as MicroStrategy who offers comparisons against Business Objects and Cognos.