Before I purchased either one of them I'd take a long hard look at the Chevy Malibu and the all new Mazda6.
The Malibu has won praise from just about every automotive publication and the new Mazda is simply gorgeous and a much better drivers car than either the Nissan or Toyota.
The Altima and Camry are both riding on old platforms that need refreshed. They offer nothing interesting in their design and nothing special in the way the way of performance.