We have all three. We have a basic tv package from BT and supplement it with the other three, giving us access to almost everything you can imagine! (except sport which we don't want)
Netflix has a lot of original series on it which tend to be good, we are transfixed by Making a Murderer at the moment. It also has some good comedy box sets. The cost of netflix can be shared with someone else as more than one person can access it at a time, so if a friend or family member also wanted netflix you could share the cost of an account.
Now TV is ok, the main draw for us is the Sky channels for Game of Thrones etc. Often the boxes are on offer in Argos or wherever and they come with x months subscription which would cost more than the monthly cost, so there are deals that can be done if you are savvy.
Amazon prime is also good, we use the Prime feature regularly for ordering from Amazon anyway, plus you get one free book per month on a kindle, so it works out OK for us. It has some pretty interesting original series like Mr Robot, The man in the high castle, Bosch etc.
I'm not sure I could choose just one (hence having all three!) but to be honest having all three and just being a bit savvy with the subscriptions is still cheaper than our Sky package was, and offers a way better choice in my view. Just make sure you have good high speed broadband!