I admire Dawkins for his passion and fearlessness. I admire Sam Harris for his brilliant ability to neutralize religious arguments and cut through to the essential issues. I admire them, really, equally well. The attacks upon them, from both the religious folk and the regressive left, annoy me greatly, and I say that as a very progressive (but not regressive-left) guy. I like Daniel Dennett for his contributions and for the charm of the man. The late Mr Hitchens made an excellent contribution to the field, and could be devastating in debate, but his political biases, apologizing for neocon causes, and attacks on progressives, left me without affection for him, I am sorry to say, though I regret his passing at a relatively young age. The higher votes for him here surprises me.
Sam Harris comes first for me as he is so calm and logical when explaining his point of view. I do love Hitch though due to the passion he brought to the debate and his refusing to deal with the stupid; that was always good entertainment. There are many others though that I also love as we get something from all of them.
Nobody could deny Hitch... but he's dead. So he's not really a "Horseman" for atheism anymore, outside of Youtube videos from the past. Therefor, I voted my second favorite, Sam Harris. It was a close decision with Dawkins, but I think Sam is a little more delicate with his interactions, and would probably be more likely to open peoples eyes without offending them and driving them deeper into stupidity.
The first Hitchens debate I saw was with his brother where I wasn't very impressed by him. I think he went easy on his brother because every debate after that Christopher wiped the floor with his theist counterpart
hitchens was great because he was able to dismember religious leaders without using science or any facts they could deny.