For several years I've been actively working with both Oracle Reports and Crystal Reports and always try to compare the tools. I didn't see any paper comparing these tools and would be interested to read such a paper myself. However, here is what I think about these tools.
1. As far as report developer tool, CR and OR are about equal, with slight more power in OR.
2. CR is easily working with any DB, while OR is primarily for Oracle DB.
3. Major Difference: CR is solely report development tool, while OR is application development tool. OR can leverage all power of PL/SQL and Java to do whatever we need with the DB. While in CR it's difficult to do any manipulations on DB side. Let's take a simple example. A report is printing invoices. You printed today invoices numbers 1 to 200, and tomorrow you want the report to pick from number 201 and continue printing. CR is extremely lame on task like this. To write someting back to the DB, a report front end is needed. For OR, to write something back to the DB is a trivial task.
4. Major Difference: CR is much muck easier to learn and use - if even OR is used only as report development tool. CR is robust, always working, and it is easy to get results quickly. OR on the contrary is very capricious, complains a lot on something being wrong with the report design, and often it is not immidiately clear what is wrong.
5. Major Similarity: neiter of the tools is object oriented, like, say, Actuate. So if you have for example 100 reports and on each you have label: "Report run on:...", and later they need to change the label to "Report executed on:...", you have go to each report and manually change the label.
