This is the consideration you will have to bear in mind whenever you buy this type of new kitchen appliance. And a lot may depend on what you are replacing.
When you duct a chimney hood to the outside, you are basically allowing all the steam and other things it sucks up to go outdoors instead of staying in the kitchen. This means it will get rid of all the smells as well. In contrast, when it re-circulates it uses a filter to clean the air before sending it back into the kitchen again.
So these are your two basic choices. The first step is to think about what you currently have in place. If your existing model is ducted outside it will be easier to do the same with the new one. This is because you will already have a hole in the wall to take the pipe through.
But of course if it is re-circulating and you want to duct your new model outside, you will have to knock a hole through and prepare it all properly to take the new extractor.
There is another consideration here too. If you want to move the design of your kitchen round, it may affect what you can have. Your extracted chimney hood needs to be placed on an outside wall for you to be able to use this method. You obviously cannot extract it if the wall happens to be an interior wall. You wouldn’t want the ducting to come out in the dining room, for example!
Having a re-circulating chimney hood shouldn’t pose any problems provided you keep the filter in good condition. Read the instructions for your particular chimney hood to see how you should change it, and how often as well. Keeping it clean enables it to capture all the smells and it will keep operating normally.
You can buy fresh filter pads in many locations, including online, so make sure you have a spare pack handy at all times. Whenever you use the last one be sure to order more so they are there when you need them.
Most people simply replace the cooker hood whenever they install a new kitchen. But if you happen to be moving into a new house where it is re-circulating and you want to duct it out, it is worth bearing all this in mind so you know where you stand.