In a forthcoming article, Nicole Garnett of Notre Dame Law School critiques form-based codes, on the reasonable ground that these codes often include meticulous aesthetic regulations that may be difficult and expensive to comply with.
However, there may be a way to supply some of the benefits of form-based codes without heavy-handed aesthetic regulation. In theory, a form-based code could be limited to verifiable characteristics such as setbacks, yard types, building height, frontage size and lot coverage.
On the positive side, a form-based code focusing on the sort of objective indicators traditionally regulated by zoning would allow a developer to build buildings that were at least somewhat compatible with the rest of a neighborhood (or with the city's vision of what a neighborhood should look like), without having to pay the costs of aesthetic regulation. For example, a city could mandate that all buildings in a neighborhood be small enough to create a dense, low-rise neighborhood, without telling the developer what the windows, facades or other architectural details should look like.
On the other hand, there may be a trade-off between flexibility and beauty: a zoning code that only addressed objective indicia of community character such as building height and width would allow the creation of buildings that on paper are compatible with a city's plan, and yet are poorly built and/or do not look particularly good.
But even such a permissive form-based code could be used to create neighborhoods that are no uglier than existing sprawl and are far more pedestrian-friendly. So for a city concerned about housing costs and burdening developers, a form-based code that does not regulate aesthetics might be an adequate compromise between a more rigorous form-based code and status quo zoning.