Chimney vs Exhaust fan.
Exhaust fan can only through the smoke out from kitchen, and not other impurities like fume, tiny oil/food particles, odor, heat that a chimney can.
A chimney is very effective. Chimneys are best option to maintain kitchen environment. One chimney will functions almost as 14 exhaust fans installed in a kitchen. And the fresh air maintained by chimney keeps your kitchen healthy too. It not only sucks the air/fume but it also traps the oil and keeps your kitchen clean.