A search on CF for
Iridium will turn up a number of threads that directly address your question in infinitesimal detail.
In summary:
1. Upfront cost is the same for
Iridium and
SSB.
2. Iridium has recurring charges
3. Little or no
learning curve on the Iridium, big
learning curve on
SSB (just read the SSB threads.)
4. Iridium is more reliable, SSB performance is subject to time of day and atmospheric conditions
5. You will want
compression software to go with the satphone for downloading GRIBs
6. You can have preprogramed
emergency numbers in the satphone and this makes it easy to send out a help if your
boat is burning or sinking.
7. You can take the sat phone in the dingy if your
boat sinks. Can't do that with an SSB
8. Can call friends and relatives anytime and instantly by using the satphone like a cel phone.
Good luck on this subject!