What is the difference between these two? Why is it when I try to download a trial of Website Forms Builder it gives me the lite version so I have no idea what the features are of the "full" version?

The lite version of Form Builder is the trail version. Form Designer doesn't have any back end scripts but there's a way to hook it to the scripts that the Form Builder uses. Form Designer has much more design power than Form Builder. I think CC is working on integrating the back end scripts but I don't have an eta.