For one thing, it would be easier to U-lock the Speed through the rear triangle: Not easy with the Mu frame. For times when I don't want to bring it into a building.

The Speed at least, looks like it has that plastic chainguard that is attached to the chainring—breakable. Mu picture not big enough to tell (assuming the pictures are accurate representations of the bicycles).

Used to be that the Speed series was made of steel too, not sure about now. The frame is only a small part of the Dahon bicycles though.