Insulsash/Schuco

FeneX, and others, what are the differences between the Insulsash and other lines of Schuco residential replacement windows?

The primary differences between the Insulsash line and the Schuco Corona 4000 are aesthetic. The Insulsash uses the Corona 2000 frame and sash and has an integrated vinyl lift rail and a concave glazing bead. The Schuco Corona 4000 has the upgraded frame and sash and powder coated steel lift handles and contoured convex glazing beads.

I see, but otherwise it's basically the same window...

Thanks!