I did both. I have an Osprey 45 that I have ran with 45s and 9. I don't have a threaded barrel for my .40 yet. I really like it, but it is a tad bulky compared to the dedicated 9 suppressors. Not having to use the extremely tall suppressor sights is a plus. I haven't tried it on my 300BLK yet. And it would not work well with my MPX. I'm very happy with it, but bought it with the intention of using it for multi calibers. If you are 100% sure you we'll never run it on something else, you may want a dedicated 9 suppressor.
I bought an Omega 9k mainly to use with my MPX. It is very small and rated for 300Blk supersonic. I imagine it will see some time on my 300 and I will try it on a 9mm. Hopefully it will be out of jail in the next few weeks.
Looking forward to the report on the Omega 9k. That's on my short list for my .300blk.