I have a TM Poseidon on my 9mm 226 and while it's a good can I would not recommend it as a first pistol suppressor. It is designed mostly as a practical suppressor - to make a certain number of gunshots hearing safe in a small package. To do this it is designed to use ablative (water or wire pulling gel) and a wipe, both of which need to be replaced regularly for the best suppression. I find that wipes and gel should be replaced after about 15-20 rounds, which means every mag or two you end up taking the can apart and replacing the wipe/gel. I would characterize the sound level as "hearing safe, but not really comfortable without ear pro".
Unless you're on a really tight budget, I would go with a full sized 9mm suppressor. You get better suppression without the on range maintenance required of the micro cans. I love my Poseidon, it's great at what it was designed to do, but to be honest since getting my full sized 9mm can the Poseidon has only had a handful of rounds put through it. The full sized can is just so much more convenient for range use.
FWIW if I were in the market for a new 9mm pistol can, I would be buying a Liberty Mystic X.
I don't have any direct experience with the rifle cans you mentioned, but in general .223s are going to be louder so I would try to get as much suppression as you can.
Another thing to look at us how you plan to use the rifle suppressor. If you're just shooting slowly from a bench you can go with a titanium can which is good for weight but bad for dealing with high levels of heat for long periods of time. If you're looking for a can to use in rapid fire or carbine classes, I would make sure that the can was rated for FA. If you ever plan to make a SBR, make sure the can is rated for short barrel lengths. Nothing sucks more than spending a bunch of money and time waiting for a transfer only to burn up your blast baffle.