IMHO, you'd be better off with a handheld VHF, since the rescuing craft will have VHF radios... not phones aboard. Between the VHF and the EPIRB, you should be covered... Sat Phones aren't all that useful once you've left the mothership.
Provided the EPIRB actually goes off, is correctly registered, and functions correctly.
A charged handheld sat phone holds plenty of battery power, and if you keep it in a Pelican case it will stay dry and functional. If your EPIRB gets away from you, a rescue craft could be chasing that signal while you float around miles away. With the phone you can also relate any injuries, missing crew, special instructions/needs etc etc. The EPIRB will only give a location.
One word of advice......don't get a Globalstar. Their satellite constellation isn't global (as the name implies), and what they have in orbit has serious issues. Here is a link straight from Globalstar, and I can confirm first hand that this issue is persistant to say the least. Their duplex data and voice systems are S#!t. They do however provide a handy tool to calculate when you might have a satellite overhead that can make your call (thanks a bunch).
Constellation Update and Advisory: News Center: Globalstar Corporate
I stand in the middle of a field (in the state of Maryland) at any given time of day and get zero service on my Globalstar hand set. On the other hand, my Iridium phone has never given me anything less than full signal. The Iridium is a fixed unit so it is inherently more powerful, regardless the signal stregnth has always been maximum since the day I installed it. Long story short, I use the globalstar as a doorstop.
Why not also pack a VHF with the raft or in the ditch bag?
I agree that when the time comes, you will get to a point where you will drop the sat phone and get in direct contact with rescue using a vhf.
PS. When I say my
phone, I mean the company. I don't personally fund two sat phones