Todd - Dave is correct. CAT 1 is manual or auto deploy and CAT 2 is manual only, but they both provide the same 406 MHz signal. Options like GPS help to provide more accurate tracking info, and the secondary 121.5 MHz signal is used for the search team to home in on your position once they get into the area. I recently bought an ACR AquaLink PLB-350C Cat 1 with the GPS option, and I bring it with me regardless of which vessel I'm on. They have a great web site and provide rescue stories that make you glad to have one on board. PLB or EPIRB provide the same signal and accuracy. EPIRB can transmit longer before the battery dies. Choice is up to you. I believe that any charter work requires the EPIRB. In your big box story above, I would have to say that the Cat 1 (manual or auto deploy) was actually cheaper than the Cat 2 (manual deploy) because of the GPS option. That would make the Cat 2 more accurate in this case and drive the price up a bit.
You guys have it right i know 6 guys and 3 boats lost to hyro not working and thats like the last 8 years and all whent down within 30 miles of home. Be safe boys