Long answer:
I'm sure that if you crunch the numbers enough and correctly, you will get a result where one class/spec combination has a higher value than others, but because of the huge number of variables, the changes Blizzard make every now and then and the fact that everyone has a different playstile, it's close to impossible to calculate and even if you could, your result would be irrelevant. No one knows the answer and no one will come with an unbiased answer, everyone will talk from experience and recommend a class/spec that suits their playstyle, but that doesn't necessarily suit yours.
Short answer: Play something that you think you will enjoy.
Cusco, thank you for your feedback and that is what i was thinking it would be like but i thought i would see what the greater whole's take on the subject was.