This is the first I've heard of WFA. From what little information I can find, the major difference, I suspect is going to be that Wonderflex has a woven netting (sort of like a single ply of cheesecloth) bonded onto one side that serves to reinforce the material and allows it to stretch more evenly along the surface as it is being thermoformed. From what I can see, WFA doesn't have this.
Sometimes that netting can be annoying, because if you stretch the wonderflex far (for more complex shapes with really tight curves), it can cause the checkerboard pattern to telegraph through the other side, giving you a square bumpy texture to the surface. It's a pain to sand/smooth this down when it happens. However, with a bit of experience, you learn to control the temperature, so this is usually not a big deal.