With the bikes side by side (see Caaah's photo), there is very little difference. The wheel base is essentially the same; as is, my rear wheel is all the way forward in the dropout, so my wheel base is a little shorter than Caaah's; but I'm pretty sure the difference is entirely within the rear dropouts. With the front wheels side by side, the headsets are also perfectly aligned side by side; but the handlebar of the Curve is a couple inches farther forward. This difference comes from the angle built into the stem. (Curve +1).
Riding the bikes, my Mini seems stiffer, on comparison to the Curve which feels more flexy. That flexiness, as far as I could tell, comes (mostly?) from the stem. Sometimes, when pedaling vigorously, I thought the stem was even creaking a little. I don't like this flexiness, but it does not feel like a serious issue. It prevented me from comparing the stiffness of other features, such as frame and seat post. Curve, by the way, has a thicker seat post which would, in theory, be a little stiffer.
Interesting Rudi. This is somewhat relevant to the recent discussion. A couple of inches forward sounds pretty good to me if it doesn't compromise the fold. I wonder what type of quill stem the Curve uses and whether it is compatible with the Mini.
Thor? Can you answer this question?