Both are great, but I give this to Smooth Criminal. In some ways the Bad scenario is really a rehash of Beat it in so many ways (Don't get me wrong, I love that video and Beat it was probably the song that hooked me into Michael Jackson period - but Bad was really Beat it part 2).
Smooth criminal is cool, the gangsters, tipping shoes and moonwalking, the dancing is out of sight and the whole thing is seriously iconic. Like you all say, the lean is easily the most iconic image of Michael as the showman created. Plus he has the patent on that shoe in which he did the lean.
Even better is to watch the whole sequence on the Moonwalker movie, Michael and the children in the city and they walk into the abandoned club and they are whisked back to the 1930s and the magic begins.
Even away from the video, the song itself is something else, probably the catchiest thing he ever made and the most iconic Post Thriller moment in his career. (Sorry but Billie Jean and Beat it, are even more iconic)