I have all three, Netflix, Amazon, Redbox.
Redbox selection is not great, but they are new. Give them a few years.
Amazon Prime does not have much good stuff in the way of "free" but you can rent for like $2 a lot of things
Netflix is still the best, especially if you like TV. Their movies are ok, but most movies I search for are not on Instant.
Walking Dead, Breaking Bad, Alias, 24, Lost, Dexter, are great. Wife has a few series she watches too.
I also click through Star Trek Next Gen and MacGuyver when she is not home.