I know a SPOT is a hands down winner for cool features, but what about in true emergency. Does anyone know of distinct advantages / disadvantages.
Oh boy. Can-of-worms time. There are proponents of both. I've written on the subject a number of times, but I'm a firm believer in PLBs over SPOT if you are only going to have one.
My reasons:
* PLB requires no subscription, part (a). Once you own the unit, its free. I've had my ACR MicrOFix for 4+ years. If I had been paying the SPOT subscription, it would have added up to be way more than my PLB, and that was back when the MicrOFix cost $700+. These days, the latest offerings from McMurdo and ACR are almost the same price as a SPOT, which means at the end of even just one year, you'll be spending more for SPOT than a PLB.
* PLB requires no subscription, part (b). With a cellular phone, the law requires that even if the phone is not activated or your two years behind on your bill, that the phone MUST still call 911. No such law applies to the SPOT device. Theoretically if you don't pay your bill, the SPOT folks could just ignore your signal. AFAIK, their Terms of Service doesn't address this possibility.
* PLB is truly global. Because the COSPAS/SARSAT constellation is operated by a coalition of friendly governments, you have reception of your 406MHz signal literally anywhere on the planet. SPOT leases bandwidth on certain birds to get their coverage. Adding coverage means they spend more money. See the "big announcement" elsewhere on this forum about SPOT adding coverage for Africa. AFAIK they still don't cover South America, most of the Pacific and Atlantic oceans, (bad for boaters and pilots), and nothing in Eastern Europe or Northern/Eastern Asia.
EDIT: Most of the Americas and Asia now covered. Hawaii and the "middle" of the big oceans still out. "Tips" of South America and Africa still out, extreme northern/southern elevations still out:
http://www.findmespot.com/en/index.php?cid=109
* PLB calls go directly to the COSPAS/SARSAT command centers. For a US-registered PLB, that means your emergency signal is seen first by the US Air and Space Command. With SPOT, your datagram goes to a SPOT call center in Houston, who will then make phone calls to "appropriate authorities". Personally, I'd rather the Airforce takes my calls...
* PLB is part of a larger signaling umbrella intended to protect aircraft, ships at sea, etc. Its use as a hand-portable device is relatively new compared to the EPIRBS, etc. carried on commercial fishing vessels, aircraft, and the like. Watch any of the episodes of "Deadliest Catch" where a crabber goes down and you'll see what a 406MHz EPIRB can do.
* PLB has a variety of signaling advantages. The 406MHz frequency can often punch through tree cover, etc. better. Moreover, most PLBs have deployable antennae instead of the built-in "patch" antenna of the SPOT.
* PLB is a regulated device. There are standards of signal strength, battery life at a given temperature, water-"proofness", etc. that a device must meet before it can be offered for sale. SPOT is basically a fancy bidirectional pager, no such standards or testing apply. I'm not even sure if SPOT devices are claimed to be waterproof or just splash-resistant?
Hope that helps.