Having ovned an Oceanis 40-2007 - and having asked for twin wheels and twin rudders for many years - or at least decent steering positions and rudder control - it is interesting to see all these new models popping up. Oceanis 38, Ovni 39, Allures 39,9, Dehler 38 etc.
Impressive new thinking, Beneteau!
You know, in what regards boat control unless the boat is really beamy (and all the boats you have mentioned are) the twin rudder is not needed for control and can even add more drag. On the type of boats that are more narrow, like mine, the First 40, the Salona 41 or the Grand Soleil 39 you will have perfect control (at least on most boats, it seems that the GS 39 is a bit nervous) with a deep single rudder.
In fact I had not yet managed to broach my boat (having always the time to let go the main sheet) even in the big gusts you get near the high coast line of Greece. I always and had a big control (and sensitivity) on the rudder and cannot complain about boat control. It makes a huge difference (for better) regarding the old Bavaria 36.
But If I could change something on my boat it would be the rudder, for a twin rudder and the wheel, for a twin wheel setup.
I am sure that I would lose some of that marvelous sensibility on the rudder but the twin wheel setup would allow me to go much faster and easier to the winches to rearrange the sail set up but most of all I would like to have a twin rudder and that has nothing to do with boat control (that is very good) but with cruising convenience.
My boat has a draft of 2.25m and that big rudder goes almost has deep as the keel, at least 2.0m maybe just a bit more. I have no problem in touching with my lead keel on the bottom at very slow speed but I have a problem in doing that with the rudder, even at slow speed. In fact I would have preferred my boat having a 2.4 or even 2.5m keel and the rudder the same size.
This is especially important in Greece where in all those little ports you lay the anchor ahead and go backwards to the quay. Many quays have enough deep two or three m away but have only 1.5 or 1.8 m on the quay and a big rudder is really not only a big disadvantage but dangerous when you move backwards.
This is for me the main advantage of twin rudders even on moderate hulls that could pass without them. They also offer an added advantage if some debris hit and break one of the rudders. The other will offer you some steerage of the boat, a perfect one on the right tack and a limited one on the other tack. Better than nothing.
Of course, it has to have some disadvantage LOL. and it has. The boat is harder to maneuver in ports or marinas...but then it is a small disadvantage and you can always have a bow thruster.