Now I'm sure both are deserving winners, but I must admit McCammon wouldn't feature on my own list. That's mainly because I've never read anything by him, which is a little strange considering the amount of horror I've read over the years.
Barker on the other hand would be a dead cert on my list for achievement in the field of horror writing, just behind King and just ahead of Herbert. I remember reading The Great and Secret Show and Weaveworld years ago and they took my breath away, the imagination displayed going so much further than many of the paperbacks I was racing my way through at the time (The Crabs for example). I'd also recommend Galilee and Coldheart Canyon which I read a few years later.
Of course Barker's influence also extends into movies, and has seen the creation of iconic figures within the pantheon of horror. The Hellraiser movies, with the unforgettable Cenobites and Pinhead, are rightly viewed as classics of the genre, as is Candyman. Fair enough, Nightbreed didn't hit the same heights, but you can't get it right every time. Pinhead and The Candyman are so iconic even none horror fans recognise the names, and quotes from the Hellraiser movies have been sampled across many musical genres, particularly hardcore and gabba. Thinking about Stephen King characters have any of his come to close to general public recognition? Pennywise perhaps?
It wouldn't be right to say Barker deserved the award and McCammon didn't, the judges know more about this stuff than I, and if it wasn't for McCammon there likely wouldn't be any Stoker Awards, so I say well done to the pair of them. It's simply that, to me, Barker has been highly influential. He's had such sights to show us.