Thank you to everybody who contributed in helping me decide whether I should make a paladin or warlock to explore the Alliance zones pre-Cataclysm. If I had just counted the "votes", the warlock would have come out on top. But it was interesting to hear that people who recently leveled a paladin thought that he'd be a good leveler too nowadays. So the decision remained hard, until more by accident than by design, I used a problem solving method called "thinking outside the box".
The principle of thinking outside the box is to first state a "box" constituting the limits within which the solution must lie. In this case I had stated those parameters, that I wanted to play one character from 1-60, on the Alliance side, either paladin or warlock. But the second part of thinking outside the box is to allow in the discussion of the problem to talk about solutions that lie outside the box, which then lead you to conclusions that allow you to find a better solution inside the box.
In this case the "out of the box" thought was a comment proposing that I should play both, paladin AND warlock. Clearly outside the parameters I had stated. But the "why not play both?" thought led to the answer that I probably wouldn't have the time pre-Cataclysm, and that one character would be enough to explore the Alliance zones of the pre-Cataclysm world. Which then led to the part of the plan that I had failed to mention, that of course POST-Cataclysm I would want to level a goblin, and possibly a worgen too, through the post-Cataclysm world to see what had changed. And suddenly the answer which class to play was perfectly clear: Neither goblin nor worgen can be paladins, but they can be warlocks. So the obvious solution is to play a paladin now, and then play the warlock after the expansion comes out with one of the new races.
But thanks again to everybody who gave feedback, even if you proposed something which I didn't end up choosing, all the comments were helpful in the decision process. And I was positively surprised about the unusually high level of feedback on the subject. Of which more, later.