I offer these to clients needing robust solutions in complex theaters and I would sum up as follows.
Sat Sleeve -
Pro cool factor. cheap(er) call rates. Increases Battery Life of phone. Can SOS call with out phone
Cons major issue is lack of waterproofing and therefore lack smart phone case to protect smart phone. Lower coverage Network (Especially the further south you go in Aus). Doesn't work in US (if you are going to go there). Eventhough Bluetooth connection still have to have in cradle.
Iridum Go -
Pro IP65, connects upto 5 devices, can be hard wired, can have external antenna...on Iridium network (Love or hate the Yankees its is the best network). Can still secure your phone in waterproof tough case
Cons Cost of calls and Data
For the 'Go' No clue on price yet but I am told it will be 'medium range'.
Pivotel who are the 'Telstra' of Satphones in Aus told me last time I chatted with the Rep that the Go is likely to be a game changer when it comes to mobile solutions, amongst other things allowing vehicles to be easily 'fitted' out with the Iridium Go and all passengers and driver hooked up to it if needed, whilst still having a portable solution should you need to leave vehicle.
Additionally if you are going overseas to, say, somewhere a satphone may be "frowned upon" the Go is a much better option to, shall we say...hide.
Also just of interest, you used to be able to keep the call cost down in Aus on Iridium casual plan as the service provider (Pivotel) didn't charge for incoming calls other than normal mobile cost....so you could send a quick 'call me' text and chat away for mobile rates....that has just changed in the last few weeks (Comes in 1st May).