It is probably self evident but the disadvantage of manual inflate vests is that if you are unconscious (think whack on the head, cold shock falling into icy water, or a heart attack) you cannot inflate the vest and you drown. This may be a fairly rare event but probably no more rare than an autoinflate vest firing at the wrong time. There are some mesh back standard vests designed for fishing (lots of pockets) that might not be too hot in the summer. No matter what you decision – wear it all the time. Every year we seem to pull more folks out who drown with the vest either left in the car or sitting in the front of the canoe.
David