Hi niko, so back more on your original question, one thing about Sweep is there is not a single "canonical" way to do sweeping, unlike something like Extrude or Revolve.

Sweep is a much more complex process that involves a kind of repeated refinement, and it's not likely that you're going to see the exact same result between 2 different programs doing the sweeping.

If you look at the surface control points, you can see that Rhino happened to generate a surface with more control points in it along what I think was your rails direction. In this particular case, that happens to make a shape that is slightly less creased to the other surface but that is more or less just a matter of luck.

- Michael