I have 3 of the Onyx and although I've never needed one to inflate for emergency there have been a few misfires. Be sure to buy several extra chargers and get good at changing them. Also, the Velcro seams that contain the air bladder - I found that if they are fully engaged they can actually be too strong and can inhibit the bladder deploying. When I say "fully engaged" the Velcro is essentially tape and if you mate them up tape to tape evenly they are very hard to tear apart. I keep mine mated together at about half the width of the Velcro surfaces and when one deploys they pop right open.
When I said there have been misfires these were caused when clients wore them while fishing /wading and accidentally caught the rip cord and popped the CO2. Once a fellow got his vest dirty and thought he would wash it off in the river which resulted in an instant deployment.
They are light and non restrictive which is good. If you are planning to use in a boat I would also keep a USCG Type 1 vest aboard also because they are not air filled and will float indefinitely. I carry both types, we wear the Onyx but have access to the Type 1's.
Ard- thanks for the feedback. I’m planning on using these when I kayak fish. A couple of potential downsides that I see are the lack of a pocket and attachment points. I think the Onyx has a d ring that I could use for a nipper and whistle. Or for the nippers I could just put them on a lanyard. I like having a pocket for my phone to take pictures. But again I could put it in a case under my seat.
Do you feel the neck yoke rubbing at all on the back of you neck? Is that made of a softer material than the bladder?
They have a fabric exterior that encases the vinyl bladder but I wouldn't call the fabric soft. I wear my own while traveling on the big rivers and almost always have a G4 jacket on or a high collar Simms Mid Weight pullover shirt.
Is your kayak a sit in or sit on type? Remember that both the brands you mentioned are auto inflators and if you get the bottom portion of the right side suspender wet she's gonna pop. Also be aware that the ripcord will set things off if you accidently pull it. The suspender types are light and allow freedom of movement but can be touchy.
I did use mine while I owned some Mokai's (jet prop kayaks) and never had an accidental inflation using them, they are a sit in kayak.
Ard - Yes I'm in a SOT kayak. I did pick up the Onyx AM-24 and you can convert to manual only by removing the bobbin and replacing the bobbin cap. I'll try this to see hoe I like it. With the humidity and temps getting higher in the mornings and being out on the water for a few hours my regular vest gets quite uncomfortable. My son and I were out Saturday morning and he kept unzipping his which does not do much good if you fall in.
I don't notice that we are getting wet at the waist so the auto inflate may be ok. I'll set it up for manual first and give it a try.
When the weather cools down I'll probably go back to my regular vest. Also if I'm fishing alone I'll probably go with my regular vest.