I was trying to load Duets in Logic Pro and got an error saying the version of Kontakt I was using was too old. The problem was that I was using Kontakt instead of Kontakt 7. Do I need to keep Kontakt (6.7.1)? Does it do anything Kontakt 7 doesn't?
Duets needs Kontakt version 7.1.5 or higher, as written on the product page.
You may need to keep Kontakt 6 installed since installing Kontakt 7 will not automatically replace Kontakt 6 content in your existing DAW projects (source).