Sorry guys I was out on a 4 day hunt for an up coming TV show on the Sportsman channel.
Between those two let me start off saying that both of those silencers are designed for limited use in "emergency" or very CQB environments. Neither one are hearing safe without water. Now having said that I would personally go with the AAC and here is why. The Poseidon will be quieter but you have to replace the wipes in the silencer after about 10 shots. With the Ti-rant you don't have to do that. So maintenance is much easier.
Now if you do want to go with the Griffin then it only adds about 1/2 an inch and gets you full auto rating, hearing safe and quiet, plus the ability to shoot 300 blackout subs. I know it wasn't on the list but I think it is a much better silencer than either of the others, for everyday use.