Hi Conor,
this is one of those things that lots of people have strong thoughts on.
We sailed for a few years in the Caribbean and then across the pacific, currently in the Med.
We used an iridium phone, hooked up to the PC and used it for emails via uuplus ( compression service, like mailasail.com)
It was flawless. We had download speeds way better than our SSb friends, we could email from everywhere. SSB users could not in certain places, through to many masts, hills or other people using the frequency etc..
Using the Iridium you also have a phone and free incoming SMS messages!.
If you shop around ( only look in the US as European dealers are way more expensive) you should be able to get 500min of time for US$99 cents per min pre paid.
The SSB is still a real must though, for talking on Net's and downloading weather faxes. We found in the pacific, GRIB files were VERY hit and miss. Learning to read a weather fax is a real plus and it helps you understand the weather movements as well. It's good to compare them and grib files.
Use the GRIBS and the FAX, Faxes are drawn up by professional forecasters that use the data from the computer models that give the GRIBs, we found that some models are better than others in certain areas, the model that gave accurate ish in the Caribbean was shocking in the Pacific. With the FAX you get the data from the GRIB and a professionals view on what it means. On the flip side some forecasters are good and some bad. Generally we were happy with them though.
Have fun on your trip!
Jason