William Lane Craig
Unless it was a bias audience.
William Lane Craig's rhetoric is based entirely on logical fallacy and bare assertion. He can't back up anything he says, and spends a great deal of time "loading" his debates. For example, in one of his debates on the validity of the "Resurrection" of Jesus, he stipulated before the debate that his opponent wasn't allowed to question the historicity of the Gospel accounts. Hello? That's what the entire debate is ABOUT.
It depends on how you define win. I have listened to most of Craig's debates and he uses the same arguments EVERY time.
Unlike William LAME, Sam's arguments are empirically supported, falsifiable, logically reasonable and truthful without ever having to rely on unjustified assertions of faith.
If you mean to ask who the audience would vote for, I think that's anyone's guess and probably depends on who the audience is. But William Lane Craig wouldn't know a valid argument if it slapped him in the face, so by any objective measure, Harris would do better.
Craig is one of the most slippery apologists I'm aware of. It's difficult for me to watch these guys obfuscate and manipulate facts to hang onto their beliefs. I don't think he is intentionally dishonest. The tortured mental gymnastics this guys has to go through to hang onto his beliefs is disconcerting. I really feel sorry for the guy. Smart people are really good at coming up with complex rationalizations to believe whatever they want.
WLC beat the pants off of Sam Harris last time he debated him. Checkmate atheists!
I think it was quite obvious Harris lost. I have atheist friends who agree.