Hi Mike
Crystal is more of Desktop Reporting directly interacting with DB mostly while BO interact with Univere(Semantic Layer before interacting with DB) .universe objects are of Business Terms rather than DB terms which helps business users to create report on scratch.
Crystal has only desktop report or web report if exported to web server which is difficult to change on web, while web intelligence of BO offers online report creation ability.
Crystal is more of pass strategy (report passing techniques) while BO has Report->Universe-DB structure
Crystal uses its own feature while in BO Desktop intelligence you can use VB macros which can extend for functionality which are not available with traditional BO
Crystal is far more rich in functions and SDK aspects while BO Reporting SDK is not much used to
Crystal is mainly used for application development platforms i.e. Java, .Net which can combine and have an enterprise level application with application-reporting while BO Reporting is only reporting
There might be many other, this has just come to my mind right now
(BOB member since 2007-08-16)