Most PLBs include some sort of life jacket mounting provisions, but this assumes an able-bodied castaway. PLBs also have to be manually activated while all EPIRBs sold in the past two decades transmit automatically when out of their bracket and wet. EPIRBs also have double the battery life — minimum 48 hours in the harshest conceivable conditions. A PLB's 24-hour battery should be plenty, unless weather prevents immediate rescue. All EPIRBs also include a strobe light to help assemble scattered castaways and increase visibility to rescuers. A few PLBs recently began to include LED strobes, which aren't quite as bright as an EPIRB's incandescent strobe light.
The biggest difference in rescue time among beacon choices comes down to $100 — the typical price increase for adding GPS into an EPIRB or PLB. Without GPS, polar-orbiting satellites compute an EPIRB's position as they pass overhead, but this often takes 90 minutes and could exceed three hours, and that position is only accurate within about two miles. With GPS EPIRBs, the beacon broadcasts its position through geostationary satellites to the RCC every 50 seconds, accurate within 100 yards.
Turner points out that Coast Guard aircraft can now hone in on the 406 MHz signal of either type of beacon. "But we can also decode the GPS position [from an EPIRB or PLB] right in the cockpit," he says. This provides pilots not just a heading to fly but also a waypoint and exact time of arrival. Those coordinates can also be read from airplanes over 100 miles away and relayed to closer rescue assets. "A GPS-equipped EPIRB takes a lot of the search out of search and rescue," Turner says. "That and [an updated EPIRB] registration are the two best ways to ensure the quickest possible rescue."
While there are only two major choices for EPIRBs — with or without built-in GPS — there are also two choices for mounting brackets. All EPIRBs activate when out of their brackets and wet. A Category I bracket houses the EPIRB in a protective shell designed to eject the beacon if the boat sinks. A Category II bracket simply stores the beacon and prevents accidental activation. While safety seems to favor the beacon automatically deployed from a Category I bracket, keep in mind that a beacon mounted near the helm where it's easy to grab is less likely to burn in a fire or be swept away in rough seas. Also realize that many outboard-powered boats contain enough floatation that they'll capsize but never sink the 13 feet required to trip the pressure-sensitive release on Category I brackets.