I don't know about the flavour because my correttos have been closed.
I roast in my backyard so the chaff lands on the lawn or garden.
I've found I can quickly lower the temperature by increasing the speed of the fan that blows away the chaff.
I don't imagine you can do that with a closed system.
You should be able to build one where you can try both open and closed systems and weigh up the pros and cons for yourself.