I do think however that at least IMHO if heritage/history were your overarching criteria, there is really only one choice:
Think about it. The wristwatch is pretty much an accessory of the 20th Century. As time moves on, more and more people will regard it as an anachronism, much as many now consider the pocket watch as such. Meanwhile, the Moon Landings will likely represent the pinnacle of historical and technical achievement during the 20th Century, and this watch is best known for going along on that ride. We should not be surprised if in some far future, would one were to look up the entry for "wristwatch" in some future ontological application, that this watch would be the first and perhaps only image they see.
Yet as we all know, there really isn't much remarkable about the Speedmaster as a watch technically or otherwise. I have one, I love it, but if I were limited to only one watch, it would not be "the one." I don't think I've figured out which one would be, personally.