kazinvan
Contributor
kidspot:Thanks for the correction...
I'm not saying that yours is one or the other, but that they really are not the same thing. Some devices seem to be a bit of both. For me, I like to have both. I have a Halcyon open circuit SMB with a pressure relief valve. It makes it very easy to inflate underwater, I can just stick the end over my reg and let the exhaust fill it up. No worries about overinflation and it's solid construction and metal buckle can make it double as a light lift bag if necessary. I also have a safety sausage. It's longer, thinner, lighter, yellow on one side, red on the other. It's a closed circuit design with oral inflation. I would use this on the surface to signal for help. Once inflated you can attach to your BC. The SMB I will try to use every few dives to make sure I'm comfortable using it, the sausage I hope I never need to use.
A lot of divers have one or the other, and many can perform both tasks but seem to sacrifice a bit in order to do so. I prefer to have both, YMMV.