I certainly don’t. I have both PLB1 & Nautilus. Each has its advantages & disadvantages.
PLB response could be delayed due to how the alert is transmitted, received & relayed. It’ll go to first to SAR satellites (some satellites, like LEOSAR may not be immediately above you, but it will orbit over your head every 90 minutes), then to Local user terminal then rebroadcast to Mission Control Center where NOAA would screen for possible false alarm or legitimate before forwarding the data to Rescue Coordination Center, which relay the data to the local SAR (USCG or Navy) to mobilize the rescue efforts.
Especially in 3rd world countries with minimal to non existence SAR services, you may not get help for days or never. However, if there are plenty of boats around to receive the VHF distress message, the Nautilus would get an immediate response.
I have been liveaboard diving all over the world. 6 out of 12 liveaboards I have been in (Spoilsport in GBR, Argo in Cocos, Nautilus Undersea in Socorro, Galápagos Master, Palau Aggressor, Maldives Aggressor) provide Nautilus for divers at free of charge. If it’s a gimmick, why would they do that?
There are 2 other liveaboards that carry similar Personal AIS Beacon that I plan to go on diving trip with them:
1. Amira to Raja Ampat, Indonesia, in January 2020. They issue ENOS for every divers on the boat.
2. Ferox to Malpelo, Colombia, date TBD
They issue McMurdo SmartFind S10, I think.