I've used Iridium--reliable for single users. But the antenna doesn't stand up to multi-person usage--it tends to get rotated out of its cup by various users and I keep having to rotate and snap it back in. Not that rugged. If you dropped it in the extended position that plastic antenna would be done for.
I really hate INMARSAT. So unreliable, spent many sleepless days troubleshooting that system. Frequent block zones, frequent dropped calls... Quirky, buggy NERA handsets, needed to be reset often, pain in the ass to use. I do not recommend.