Even if you have a small engined petrol auto, there’s still an advantage. You don’t have to change gear.. obviously. Especially nice in traffic jams.
Re DSGs – SOME have better CO2 than the manuals, some do not. The better ones are the 7 speed dry-clutch ones which afaik you only get on smaller engined petrol cars. Having 7 gears means it stays in the most efficient power band more often, and the dry clutch means there’s mechanically no difference between it and a manual.
Btw, even if they do have flappy paddles they still have an auto mode which you would use almost all the time probably, unless you are a boy racer and pin it everywhere. And conversely, even without flappy paddles you still have a manual mode operated via the normal shift lever.