Hoods are the hardest thing to buy, because the residential hood companies are mostly peddling nonsense and the commercial companies won't talk to you.
Most of the conventional wisdom is wrong or misleading. Cubic feet per minute of air flow is not a useful measurement for much; there's no way to translate BTUs/hr of range power to CuF/m. The important factors are range dimensions and basic hood design, particularly the geometry and the cubic feet of hood capture area—a specification I've seen mentioned exactly never by a domestic hood company.
Here's the best short summary of how to design a hood system that I've found. Here's a longer version (scroll past the health scare part). If you figure out an easy way to translate this into a purchase and design decision, please share!
