I have or do own every brand that you are considering. My go to primary regulators were Poseidon for the last few decades, now my primary regulator is Deep 6. Full disclosure, Chris, is a friend of mine. I won't and don't allow friendship to influence my gear choices though. Chris, the owner of Deep 6, has forgotten more about regulators than I will ever know. When he owned HOG I also got a couple of those regulators however I only have used them at backup stage regs. The HOG's are good regs but not great. The Deep 6 are as good and in many ways better than my Poseidon's.
A couple of things that stand out on the Deep 6 regs for me. The lp swivel extending out a little further makes side mount diving just a bit cleaner. On back mount the 5th lp hole on the bottom of the turret makes hose routing a little cleaner. I haven't mounted the Deep 6 regs on my CCR yet and don't know if I will, the CCR runs at a lower IP and I have a fairly complex arrangement that would take some work to reconfigure for the Deep 6 regs. The reason I'm considering doing it is to reduce the amount of rebuild kits I carry.
The most important reason that I prefer the Deep 6 regs is quality. When I first received them I tested and adjusted the IP on all of them, then chose one to completely disassemble one to see the quality and internal workings. Chris took the time and money to improve and use higher quality parts in critical areas that other manufacturers don't. The Deep 6 regs are also the only reg I've completely disassembled and reassembled without having to tweak the IP. I have not needed to rebuild them after more than two years of using them as my primary regulators, however they are straight forward and won't be hard to rebuild. Any shop that works on mainstream regulators will be able to rebuild these for you or you can learn to do it yourself.
I like the older, heavier, regulators. I'm rough on my equipment and the lighter, thinner walled, regulators don't hold up as well. The Deep 6 regulators are beefy and will/have taken my abuse. For those that don't have connections inside the dive industry the fact that you can purchase rebuild kits as a consumer is another plus. I can go out and buy brake parts for my truck and replace them myself, which if I do wrong can not only kill me but others on the road as well. I've always thought it hypocritical that regulator manufacturers won't allow the end user to purchase parts to rebuild the equipment that they own.