I hate to say "it depends" but it does. They come with some very nice, thin insoles. I wear them without insoles; they're designed to work well both ways, depending on user preference. I like to be as near to the ground as I can.
Without insoles, it essentially makes them work for wider feet because you've opened up the amount of room, and the two models I have are both very flexible, so opening up more space allows your foot to spread out. With the insoles in, they would tighten up and work for a narrower foot.
I don't know if that helps at all. I am normally a 10.5 with slightly wider than average feet, and I went with a size 43-euro, which was too tight with insoles and perfect without them.
I think I would have been fine a size larger as well... definitely with the insoles in. So there is a little margin for error.
Hope that helps.