I am biased because we have a sat phone (Iridium), and without sounding dramatic it saved my leg and possibly my life. Every situation is different, but in an emergency I don't think there is any substitute for having instantaneous two way communication. It can truly be crucial to making the best possible decisions, particularly under less than ideal conditions. I would never want to be stuck pushing the sos button and hoping that someone was receiving my message, and that help was in fact on the way. Or not on the way, if weather is too bad and we need to move to plan b and shelter in place.
Two way texting feature is certainly better than nothing, but I still think there is the potential for meaning/information to be lost. How often do you read a text message and have trouble understanding the context/intent of the person who sent the text? It happens to me all the time, and these are in conversations that aren't crucially important. Now imagine that in a life or death sort of emergency, where you or your partner are under high stress...
I suppose I am paranoid, but we don't travel out of cell range without the sat phone. Sure its not inexpensive, but in an emergency it's so worth it...