1st stage type
A piston 1st stage is easier to service, since there are less parts. However, a piston 1st stage needs to be serviced earlier than other 1st stages, since the water does get inside the 1st stage. A membrane 1st stage may be less maintanace- sensitive, however, you’ll have to be more precise in adjusting it. If you would like to dive in cold(er) waters, we would recommend a 1st stage with a membrane.