An exhaust fan pulls the smoke in one place without a duct. This allows the smoke to interact with other kitchen elements.
In case of the Kitchen chimney the smoke is sucked into a duct directly above the hob/stove and does not interact with any other kitchen components.
Average Power Consumption
Exhaust Fan -80 Watt
Kitchen chimney - 200 Watt
Average noise
Exhaust Fan -40dB
Kitchen chimney - 58dB