Why Steak (over Cucumber)
Plain text have no value if people writing and reading the specs are developers. Code is natural language for developers (specially if that code is Ruby). Having a client who reads the specs is a possible situation and Cucumber is cool there, but in my experience that situation is not the most common one. If in your case there's no value in having your specs in English rather than in Ruby, Cucumber is an additional layer of abstraction in exchange of nothing.
There's a myth about clients writing the specs. It sounds like a unicorn to me, but let's take it. Still, I wouldn't want it. Clients are experts in problems, I am expert in solutions. I want the client to describe the problem I have to solve, not to describe the solution.
Some people say Cucumber is cool because you write the stories, the client validates them, and then you can start developing. That is not Agile. The on