Over the years I’ve had a lots of experience with most of the top-line satellite phones including the original iSatPhonePro, the Iridium 9555, the Iridium Extreme 9575 as well as the new iSatPhonePro 2. After using them all I can tell you from real-world experience which one is the best all-around phone to have on-board.
As you can imagine you can find all sorts of ways to use a satellite phone while offshore some of which are for life-safety issues like weather and medical but most are something as simple as email to the family or calling ahead to a marina for a berth.
I bought my original iSatPhonePro at the Dusseldorf Boat Show back in February of 2011. It had just been introduced and claimed to be far superior to the offering from Iridium. At the time I think I paid about €550 for the phone and a show special of about $0.80 per minute for calls. Compared to the Iridium 9555 it looked more modern and claimed to have better voice quality. After using it for quite a while I had to agree the voice quality was good and better than Iridium however it took forever to lock onto the Inmarsat satellite system and that proved to be a big problem when you needed to do a quick call for tech support or medical support while offshore.
In 2013 I purchased the new Iridium Extreme 9575 which had good reviews for start up time, voice quality and the cost of prepaid minutes. I have used it for the past year and half and been very disappointed in the voice quality and the ability to hold onto a call without dropping. I had purchased an external antenna mounted on the back of the yacht to provide the best signal strength and even using that the calls where mostly garbled and unusable. The other crew members also have tried it over the past two years to call family/friends from time to time and each of them are as disappointed as me. In short, in our opinion, the Iridium experience is not worth pursuing.
Just this month I purchased the new iSatPhonePro 2 and it appears they have addressed earlier concerns and this, finally, is the satellite phone to have. I will use it across the Pacific for our main form of telecommunications and by the time we reach New Zealand I'll let you know if I've changed my mind or not. So far, the crew agrees this phone is the best one we've had.
For now, I'm very pleased at the improvements. The start-up time to acquire a GPS connection and register with the Inmarsat system has been greatly improved and the larger battery provides increased talk-time. In using the unit for voice communications it has clearly exceeded the experience I had before, although we still have the 'lag time' for the signal to travel from ground to satellite to ground again which can not be improved on and is present in all satellite phones.
In summary, the latest iSatPhone 2 is the best satellite phone available right now. However, both Iridium and Inmarsat are in the process of putting up new arrays of satellites and, in the coming 3-5 years, I expect to see more improvements in satellite telecommunications.
If you are interested to learn about using a satellite phone for downloading grib files or doing email, I wrote an article, Email, weather and gribs at sea using a Satellite Phone about that a few years back that is still correct today.