What's the recipe for creating a niche coupe, using two of America's perennial top-selling sedans as a base? Lose the rear doors, craft an attractive rear end, and offer an optional manual gearbox to please enthusiasts. But unlike purpose-driven performance coupes such as the Chevrolet Camaro and Ford Mustang, sedan-based coupes must capture the essence of the four-door original in order to carry its fan base. As recently as two years ago, the list of two-door iterations of sedans included entries from Toyota, Chevrolet, and Chrysler. Since then, however, the field of midsize coupes has shrunk to a number you can count on one hand. And with two of the standouts, the 2011 Honda Accord and Nissan Altima coupes, remarkably similar in terms of dimensions, horsepower, and price point, we decided to see how each manufacturer applies the tried-and-true formula.