Hi Felix, also see this previous post for a bit of explanation on the differences between Sweep and Network:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3081.23

There are several situations where you can use the same curve setup for either one, but they create the surface in somewhat different ways.

Sweep works by actually sliding the profile along the rails - it will tend to maintain a more rigid shape of the profile.

- Michael