Hi Auraele,
Advantages some times are to close to personal preferences but in my point of view Crystal offers you a user-friendlier interface to create and modify reports.
The graphics features that allow you to alter reports while in presentation mode are great. You really can change your report so it appears exactly (or really close) to what you want.
The sub-report resource allows you to create summaries or access data to table that do not have a direct relationship with the ones you are using in the main report.
Talking about relationships Crystal allows you to create new links for your tables, I mean, if you need to connect tables that usually do not have a relationship in your Access database you can create those links specifically for each report without changing the structure of your database.
And these are just a few advantages…
Hope it helps.