yes thanks, and I know you can't home to them like you can with a 121.5 emitting 406 beacon. You also can't home to a 406 beacon because it isn't a constant transmission, just a burst transmission every 50-odd seconds or so - that's why they tx on 121.5 as well.
PLBs/ELTs on 406 don't need subscriptions and have better coverage than personal sat-trackers
This sort of thing is actually my specialty. My main work is producing complex RF systems. There is some detail lacking here that it might be helpful to fill in.
As crab correctly states, the 121.5MHz signal is required for conventional (practically "classical" at this late date) homing, aka direction finding. There are some subtleties here associated with more complex equipment that could actually geolocate 406MHz bursts, but such capability is rarely found in a SAR operation.
However, and most important, there are two types of 406 beacons. The first only transmits an identifier that, if properly registered, identifies the aircraft specifically. This is a great help in resolving false alarms, but does not improve the satellite-based geolocation performance much above that provided by the older 121.5MHz-only ELTs. These 406MHz signals require many tens of minutes to sometimes hours to geolocate, the same as the old 121.5MHz signals. And geolocation accuracy is poor, typically resulting in a 4KM radius to search, again similar to the 121.5 beacons.
The second type of 406 beacon incorporates either an interface to an external positioning system, usually GPS, or an integral positioning system, again GPS.
Such ELTs completely eliminate the requirement for homing. They transmit a precise position to the Cospas-Sarsat system, with accuracy of well inside a 100M radius, and do this within just a few minutes at most. This position is then relayed to SAR assets. They are thereby a huge step up from the non-GPS equipped or interfaced 406 beacons. Indeed, these days it is sheer folly to not be so equipped. And yet most aircraft ELTs in general aviation are of the older, non-GPS equipped 406MHz type.
As in much of aviation, regulatory aspects are cost drivers and prevent rapid innovation. Hence, as crab and I both have already suggested, obtaining a modern PLB, which will undoubtedly include a built-in GPS positioner, is of very high value.
This brings us to the statement above regarding "personal sat-trackers", more properly called "satellite communicators". While it is true that these do require a service plan similar to a mobile phone, you do get what you pay for. They provide functionality over and above PLB/ELT/EPIRB systems, most notably two-way text messaging and periodic tracking updates a la Spidertracks and other similar, commercial tracking services. With respect to their coverage they actually can perform better than the Cospas-Sarsat system. If you are down in a canyon or other steep territory, it is possible that the GEOSAR satellites will not be in your field of view. In such a case you have to wait for a MEOSAR or LEOSAR pass to see (have radiofrequency line of sight to) your beacon. That can sometimes take hours, depending on the present geometry of the Cospas-Sarsat satellites. The same is not true with satellite communicators (or the commercial sat-tracker systems). These all rely on either the Iridium or Globalstar constellations. Both of these systems use a great many satellites in low Earth orbit, and thus passes over steep terrain will occur much more frequently. When choosing between the two systems the only thing to consider is that there is no polar coverage for Globalstar, while Iridium has complete global coverage. Bottom line: commercial satellite communicators, in particular those using Iridium, and specifically the Garmin inReach products, are the gold standard for rescue communications and location, lacking only G-switch activation. The lowest priced plan in the US is about $140USD a year if you never send or receive any text messages or send any routing position reports.
Of course the best answer is to "get both". And carry other tools to get found fast and solve the last 100M problem, such as whistles, mirrors, lights, handheld aviation radios, etc.