I have GlobalStar and have seen it go from being very good several years ago, to horrible a couple years ago, now back to okay at best. I use it in the Bahamas 3-4 months every year, every day, and it does get frustrating waiting for connections and seeing them drop after 10 seconds. It is way less $ than Iridium, but for a reason. I've learned to live with the G* phone, but it does not hold a candle to Iridium. For a short amount of time, get the Iridium with the Ocens package and forget about the SSB ... too expensive, a complicated install and it'll take you weeks to figure it all out.

Just make sure you test it all out before you leave, make sure you have the right softwares for the computer and it all works nicely before you cast off.

Have fun, cheers, John