Vamp and Runway are quite similar. The only difference is that Runway has the contrast color in the lining (beige) making the X in the tummy visible. Runway is also black through the back side of the garment (just like Vamp).
It's really a style preference - Runway's X is flattering because it follows the shape of an hourglass, and we've been told it looks more stylish than existing shapewear. Vamp is a simple, clean, all black design.
Either way, you can't go wrong :)