NPR was saying that Netflix accounts for (iirc) over 30% of internet usage evenings in the US. That is a huge number. Then there was discussion about exclusive titles in the competition between Netflix, Amazon Prime, and Hulu. In the end I suspect one will survive (either by buying the others or driving them into bankruptcy). Netflix has the early lead, but Amazon probably has the edge in the long run due to their much deeper pockets (due, in large part to shareholders that don't seem to care about profitability).
There is a limited amount of time and a huge amount of programming available on any one of them, so I see no need to pay for more than one. It probably doesn't matter much to consumers who wins: we get excellent value while the competition is on, and that will likely go away somewhat once the winner is decided. Still, Amazon does seem to be taking over the world, and I would like to think that there is room for other people selling things on/over the internet...but they really do have the best overall deal, provided you order other things from Amazon.