It's no secret that classes and specs are not the same when it comes to the likelihood of getting Gladiator or raiding all the way to Kil'Jaeden. You may love your Hunter, but arena's not that kind to them at present. Your Warlock might be endless fun to play, but the guilds on your realm are probably swimming in them. And if you've ever cruised past the recruitment forums, you've probably noticed that they all seem to want the same thing: healers (and lots of 'em). If you were the sort of person who sat down, looked at the content in the game that you wanted to see more than anything else, and picked your class and spec solely with that goal in mind, your path forward would be fairly clear...but you might also become one of those people who logs off their primary toon as fast as they can after raid, or after their 10 games for the week, and goes to play the alt they'd secretly love to be playing as a main.
Ideally we get the perfect intersection of a class we love to play that's able to accomplish its goals in content we want to experience, but it doesn't always happen -- and if you have to choose, the decision is a pretty personal one. So I ask you: class or content?