We have 7 Twizys and all have doors except the one I use myself. We chose to do that to see what it was like and because we were really interested in what a minimalist car would be like, because we felt that the more like a car you make something like a Twizy, the more you would start to compare it with a ‘proper’ car and find it wanting! But we have driven both kinds extensively and our (biassed) conclusion is that the doorless one is quieter and more conventient to get into and out of and (provided you have mud flaps) actually drier most of the time. I say most of the time because without doors you can get splashed by other road users if you’re very unlucky - I think it’s happened to us once. The reason is that rain drips off the roof and falls INSIDE the doors if you have them, placing a damp surface next top you while you’re driving.
The only time we would prefer having doors is when carrying luggage or a dog. Then the floor on the near side provides useful extra space. Also, a closed door probably provides some greater security when parked in town - though for greater peace of mind you would then need to get windows as well, which we found to be quite claustrophobic when we tried them. This isn’t a great issue for us out here in the country where there are fewer people and you tend to know more of them anyway.