Curious, have you considered Media Pro + C1 (round trip via "empty" C1 sessions, as described on the Media Pro forums)? Or does Media Pro not have certain DAM features you need?
As the person who drove that thread about using an empty session, which at the time I thought was the solution, I now have to raise two issues with it.
1. Phase One broke the integration between Media Pro and Capture One when they released V10 of Capture One. I raised this as a "bug" during the beta of C1v10 (Phase one didn't respond) and others have raised it since the release - but its still broken. You can still share metadata, but Media Pro no longer sees the C1 edits. The MP previews are still generated with C1, so they look like the previews generated in C1, but don't show any edits.
2. The empty session idea uses a virtual link to the Raw file which means that the edit with option (i.e. editing with Photoshop) doesn't work with "empty sessions".
Two other issues that have disillusioned me a bit are:
1.When the empty session thread was live I contacted Phase one to ask them why they didn't formally promote this approach to integration, and pointed them to the thread. They looked at the thread, sounded positive about it, and agreed to produce some tutorials/webinars based on the thread - but nothing has happened.
2. In August 2016 I identified a bug that prevented me viewing *.mov files in Media Pro. Phase One agreed it was a bug, but 7-8 months later it still hasn't been fixed and I have had to look elsewhere for a DAM solution.
Media pro is an excellent DAM at its core, but it needs updated, and it seems obvious that Phase One have no real interest in it or in meeting their advertising claim of integration with C1.
I now use C1 catalogues (one for each year) and just use Media Pro as a "Master catalogue" with no attempt to integrate with C1, other than metadata, but then C1 can share meta data with any program that can read XMP files (actually MP and C1 share some extra colour labels).
C1 cataloguing slowly improves with each point release, and although clumsy compared to a DAM, it is very fast once loaded (faster than Lightroom for me) and it works fine as a low level DAM for managing files while processing.
I've recently started to use NeoFinder as a DAM, which is deceptively powerful. It also looks as if the PhotoMechanic DAM is getting closer, and as I already use Photo Mechanic, that might well be where I end up.
C1 is great, and there is no prospect of me giving it up, but Phase one have been a great disappointment in their approach to Media Pro, nd the empty session solution, isn't really a solution at all :-(