>>183012GPS is good to ±8meters.
Precision improves if the unit isn't moving.
Things like DGPS (WAAS/EGNOS) and averaging can get you down to ±2m.
121.5MHz (VHF) beacons are ±10km (about 5 miles).
406MHz (UHF) beacons get you ±2km (1mi).
Most PLBs have both VHF and UHF, as well as GPS. When you first power up the beacon in an emergency it broadcasts the VHF/UHF signals to satellites. Once GPS has a fix, those coordinates are relayed with the VHF/UHF messages. The longer it stays in one position, the better the location fix.
SPOT is GPS-only - SAR cannot triangulate a position from a SPOT beacon without GPS. It also goes through a different set of satellites, relying on SPOT's ground operators to relay emergency information to officials.
SPOT has tracking and check-in messages... PLB doesn't. If you want this feature, SPOT is the way to go.
If you want a solid tool to alert and activate SAR when something goes horribly wrong... PLB is the way to go.
I'll be getting a PLB in the next few months (ACR ResQLink).
I do have and carry several radios with me - FRS is usually used within our group since everyone has one and they're cheap. An unlocked ham radio can do pretty much everything provided you know how to use it.
Avalanche beacons are completely different - their use is within your group. Turn them on at the parking lot, leave them in transmit mode while you're riding, turn them off when you're back at the truck. If your riding buddies don't have and know how to use a beacon, yours is only going to help rescuers find your body. Time is critical with avalanches.
Pic related; radio, GPS, and avy beacon.
