Hmm, did your bernina dealer tell you this? When I bought my first Viking machine with an embroidery module, my dealer told me to only use Viking embroidery files, which were much more expensive and only available at the dealer's store. Embroidery library files worked just fine. Here's a link to a review which specifically talks about how nice the 780 embroiders emblibrary files...
http://sewing.craftgossip.com/review...-3/2012/11/15/