What percentage of your users are Catia and what percentage are Creo. windchill works better with creo and that is what I recommend
This should have been opened as a new thread, not hung off a 5 year old one!
CAD and PLM have changed significantly in 5 years.
Both programs are capable of storing data from the other CAD system. The problem with a third-party PLM is waiting for an update and synchronizing your updates so everyone is working together.
Using 2 different systems for the different types of CAD files will be a pain. Which system does the user need to look at? When you make changes to one can you make the same change to the other? It's will be a pain to keep 2 systems maintained.