Looking at this thread with some interest.
I have been sailing boats / sail boards / land yachts for the last 40 years , have been a very active kite boarder for the past 10 years . Have had a great deal of experience with both inflatable and foil kites.
As mentioned there are definite pros and cons for both types of kites. To get something efficient and well developed performance and safety wise , you would have to go with a well known kite brand , someone who has put in the development and research.
pros / cons
Inflatables are safer when it comes to dropping them in the drink , they float as long as there is air in the bladder , a foil kite will be ok if relaunched fairly quickly , my experience if it in the drink more than about 10 mins , you have a massive sea anchor on your hands , if this happens on a boat that would pretty much be the end of that kite . Imagine a double skinned spinnaker , with cells inside full of water .
The down side of the inflatables is that they need to be pumped up manually , the foil kite will self inflate , another issue with the inflatable kites is the reliability of the bladders , they are fairly robust in a kite surfing application , but when it comes to heavy yachts , not sure on the longevity of these , they need to be constructed light so the kite will fly, if a bladderer was to burst the kite won't fly , you would have to be very carefull moving it around on the deck and setting and packing up . If it was to drag across a shackle or a horn cleat , it would be finished,
A down side to the foil kites are the dozens of lines they require for the bridals to support the kite, inflatable kites have minimal or no complicated bridals . Thesebridals are a nightmare when working with the kite on the deck and launching and landing ,
Both have similar power and depower , foil kites are a bit more efficient , inflatables a little more user friendly.
Not sure how to successfully launch and retrieve either a inflato or foil kite off a boat , you would need some type of mast ( maybe telescopic ) to raise to centre leading edge of the kite up , and once in position pay it out with some sort of winch system out on its 4 lines. And the opposite to retrieve.
My choice would be a foil kite , because of the ease of inflation and the questionable reliability of the bladder system.
Flysurfer are probably the leader in foil kite development , they make a 21 or 24m kite off the shelf , they also make a single skin foil kite , used mainly for snow kiting , if you could work out how to keep this out of the water this would be ideal .
Other issue with a kite over a conventional rig is that the kite requires constant input , the conventional sails you can set them , cleat them off and go about your business , a kite needs someone flying it the whole time , some of the big ships which use kite as a fuel saver , have computers which automatically fly the kite.
For a cruising boat your talking a hell of a lot of stuffing around .
The application I can see these kites being used is like the big ships which use them . I can invisage and big power cat , like the ones you see fairly commonly getting around 35-50 footing ,the kite could be used for longer passages with favourable wind direction and strength to reduce fuel consumption .
Another use could be for racing boats ect , if you were to break a mast or something , you could set one of these to help get you home.
They take up bigger all room and are light.
The application for an everyday sail replacing a conventional rig is a fair way off I think.
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