It seems to me a bit of mismatch: McGrath is intelligent, moderate, and sometimes engages sympathy. Part of his problem as a debater is that he has both a waffly style - he's too gentle and indirect, with expressions such as "What I think I'd like to say to that is ..." - and some unfortunate mannerisms. This can be off-putting, can distract from whatever substance there might be in his arguments.
By contrast, Hitchens is a superb live debater with a bulldozing style. He also had a strong set of points to make, and was obviously comfortable with them all. He's made these points so many times by now that the presentation of them has evolved into a very powerful form. You'd think he'd be getting bored making them over and over, as he debates various opponents, but in this presentation there's no sign of it.
One point that I always find annoying in such debates is that the religious apologist inevitably brings up the old canard about the supposed need for a metaphysical grounding for morality. The non-believer then suggests some kind of naturalistic grounding, based in evolutionary psychology or social necessity, or whatever. Nothing is ever clarified. In fact, it's not at all obvious either that morality needs any metaphysical grounding or that any naturalistic grounding it has is just one thing. The story may be quite complex, and secular moral philosophy and moral psychology are still working it out. That doesn't detract from the widespread practical agreement on at least some core moral ideas, or from the fact that we need morality to meet certain human interests, even if nailing down the exact nature of those interests (and the exact nature of the morality we need) is difficult. Moreover, no religious apologist has ever told a sensible story as to how morality could have a philosophical grounding even if a being like the Christian deity existed.
The whole issue of moral arguments in support of God's existence is such a red herring. The truth of it, I suppose, is that there are people who crave a simple support for their moral beliefs, and want no complications or uncertainties. There's a fear out there that religion plays upon. To borrow an image from somewhere in John Barth's oeuvre, we're like Loony Tunes characters who have run off the edge of the cliff. When we moralise, we're suspended in thin air, with nothing beneath to hold us up. Or so the fear goes. But that's the wrong way to think about morality: it's something we create, socially, but to meet real needs. It's not just arbitrary, leaving us hanging in air, and that's not the only alternative to a religious account.
Anyway, Hitchens won this debate quite clearly - certainly at the level of performance, and I think at the intellectual level as well.