You are right it is a growing market and is the future.
To the best of my knowledge the the important patents are held by the 3 companies mentioned.
All others are really badged versions for local markets.
I am sure that in real terms they all work well,the best local aftersales backup is probably the deciding factor for you.
The more interesting issue would be how much extra would these companies make if they sold the rights to mainstream manufacturers.
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