My recent experience with the Sachs Duomatic, is that it’s a very high quality hub that works really well.
But, I find myself wishing that it had that third gear ratio in between the high and the low.
The low gear is slightly too low, and the high gear is slightly too high, so something in between would balance the spread, and keep you from reaching for that sweet spot that just isn’t there.
Changing the cog/sprockets isn’t really much of an option, because your still adversely affecting one side or the other to get that one gear that is more to your liking.
The New Departure two speed is a good set up, that works with a normal single speed type ratio, but gives you that low granny gear for climbing hills, or pedaling into the wind.
It’s a good time tested system that works surprisingly well.
I used to have a Shelby with the New Departure Triplspeed, and I’ve got to say, that I liked it the best.
I’ve always wanted to build up another bike with one of those.
They weren’t introduced until 1950, so they are a little late for the type of bikes I collect, but the function was the best of all the classic era multi geared set ups that I have tried.