I’m afraid you’re going to get one of those irritating, and generic answers from me. But it really does depend on how you play the class. I think ANet has done a really good job in balancing them (by and large – engineer still need some scrubbing up…).
If you spec, and play the character well (which means adapting your play style/tactics for every character or opponent you come up against) then I believe it is genuinely a case of skill vs. skill.