The ADV on my Pelagian is just some second stage guts built into the top of the head. You can roll on your back and the thing will freeflow since it's hydrostatic, but when you're in trim, you do have to suck. Lots of guys will pull the guts out, blank the top, and run it with an aftermarket MAV.
The SF2 is second stage guts inside the top of the CL like the RB80's. You've gotta bottom out the CL to get it to fire.
Both can leak since they're both essentially just a second stage, but like anything else rebreather related, some judicious maintenance and proactive attention should prevent it. I trust them both enough that I find the benefits of a gag strap outweigh the rather small risk of hypoxic dil leakage. That being said, I have a shutoff on my SF2 and I use it.
The SF2 is second stage guts inside the top of the CL like the RB80's. You've gotta bottom out the CL to get it to fire.
Both can leak since they're both essentially just a second stage, but like anything else rebreather related, some judicious maintenance and proactive attention should prevent it. I trust them both enough that I find the benefits of a gag strap outweigh the rather small risk of hypoxic dil leakage. That being said, I have a shutoff on my SF2 and I use it.