I'm a big fan of both. Murakami has a superhuman imagination. I love the way he weaves magical realism into his stories and pulls the rug out from under the readers' feet. I hope he wins the Nobel, too.
I just think that if there are more casual readers watching the Literature prize this year (I suspect there are), then Ishiguro is the perfect writer to make the most out of that increased attention. Anyone who has ever read a book can pick up Never Let Me Go or The Remains of the Day and be hooked. Murakami can be a bit challenging if you don't know what to expect.