Immarsat seems to be the way to go in terms of service, coverage and company stability. But it really depends on where you'll be, doesn't it? Also, I believe the Immarsat antennas are the largest, and you might not have the space on deck, rail or arch for their domes.
Globalstar, irrespective of their satellite issues, is primarily a North America/Caribbean service. I would think there's enough opportunity to just pull into a serviced marina and scoff some wireless access to get data, just as cell phone service is available many places. At the prices you are considering, you are well within the "price point" of a top-end SSB radio and Pactor modem set-up, which would be my choice as the ongoing costs are minimal and the system itself is virtually world-wide under most TX/RX conditions.
The qualifications for marine SSB usage aren't nearly as onerous as they once were, and many people are now opting for the full amateur radio licence, meaning that instead of a "dedicated" marine SSB like the new ICOMs, they can get much cheaper ham rigs like the Kenwood TS50S, which are very durable and cover a greater range of frequencies.
Just my .02.