It's a complicated subject. In a limitless World you would have a SPOT, InReach, PLB, Sat-Phone, cell phone, handheld aviation radio, EPirb, and a 406 ELT. Each one has it pluses and minuses. You have to decide on the mission, costs and functionality. I personally carry a cell phone and SPOT and have a 406 ELT. I used to have a Sat-phone, too. I've gotten very close to switching to an InReach, especially since Garmin bought them out.
I prefer the active tracking of SPOT and InReach. It's something I can use and test EVERY DAY, flying, hiking, boating, or on a road trip. They have "the button" for the big rescue, but they are always passively protecting you with the trail. If something happens too quick to hit "the button", at least they'll know where the trail stops. The InReach goes one step farther, allowing you to TXT with rescuers, or maybe just a friend who needs to bring you a new tire. The InReach also uses the Iridium network, with has better coverage Worldwide.
The PLB do what they do very effectively at a good price. But you can't use it every day, or even test some of them at all. The cost of the battery is such that a lot of people just buy a new one every 5 years. Because it's a dedicated device, there is a very good chance it's going to going to get you rescued.
Ultimately, all of the devices will eventually end up generating a phone call to the local Sheriff, State troopers, SAR, or the military