Orbcomm uses a LEO satellite system like Iridium, but it uses fewer satellites than are needed for full global coverage. Instead I think they chuck them into eliptical orbits so that you kind of get decent coverage, but not all the time (be aware of that limitation)
They seem pretty expensive for data, but like with everything it's going to depend on your usage as to whether it works out cheaper or not
Do bear in mind that a sat phone system like Iridium really is a full telephone and internet connection, not just a limited messaging platform. So you can send relatively large emails and also pickup the phone and talk to people
Horse for courses and all that
Good luck
Ed W
P.S. There are some rumours that Orbcomm are hoping to be bought by Iridium. Iridium claim to be surprised by that...