rspec + capybara is much more enjoyable and maintainable. Maintaining a cucumber test suit is basically a nightmare. I hate writing tests for it, I hate fixing tests in it when they break, and i hate the random cucumber exceptions that cause random failures. and should you come to a point where you want to optimize the test suit performance, good luck!
cucumber is good if you're not the one writing or maintaining the tests. You just have to have a DSL that the test maintainers can use, and they handle writing and maintaining. But thats it.
If the devs are the ones who have to write the tests, as is far more common; then interfacing with capybara directly is much much better than bringing cucumber into the mix. I used to be into cucumber, but once i switched over to a leaner approach i found testing was much easier and more enjoyable.