What class is better a rogue or a warrior in wow?

Which class is better than another class is totally dependent on what you are wanting to do with it. Once that decision is made, then it comes down to your play style, and finally how good you are at each class.

For example, a really good rogue can beat a decent warrior any day, then again, that same warrior once he gets better gear and better at his class could just possible beat the rogue.

It mostly comes down to gear, and skill, not which class is better.