There is no way the Batman can be considered an antihero. I think he attracts this kind of label because of the grim angsty Dark Avenger image that hangs around him, especially since the recent movies have played up that side of him rather than focusing on the aspects of his character such as being the greatest detective in the business. He is indeed a serious individual, and not to be crossed, but his morality could hardly be more starkly black and white. His entire motivation is to stop evil being done to the innocent, and if necessary he would sacrifice his life for that without regret. And while he certainly does play hard, he never crosses the line.
Wolverine, as you say, is a much better example. He is an outright killer, and not particularly worried about that. Whereas the Batman would tell a criminal they were in for a savage beating if they didn't give up the required information (and mean it, and do it), Wolverine would simply make it clear that they were risking their life by holding out. I have a distinct memory of Wolverine looking up at some much larger adversary, and telling him that by crossing the X-Men he'd made the worst mistake of his life - "And the last."