From what I've read, the Sonata Hybrid delivers quite a bit better fuel economy than the Camry Hybrid, but that's something hard to substantiate without direct comparisons between the two.
Don't forget the Optima Hybrid too... same powertrain as the Sonata, slightly different features/packaging, vastly different style and maybe differences in price too. I personally prefer the look of the Optima, but it's very subjective!