Looks like they are trying at least two different spoilers along with the side skirts. The one on the silver one is smaller and smooth across the top, the red has an indent in the center.
The silver one looks amazing. I can't tell if it's the lighting or not but the silver valences also look black, or at least darker. This looks infinitely better to me than the grayish coloring. It also makes the body colored rear diffuser look a lot better.
I don't think they've nailed the perfect spoiler yet. If I had to choose one of the two options the silver car would get my vote.
The silver GT with the different spoiler also doesn't have the GT specific brakes. GT's are supposed to come with 4-pot calipers standard and 6-pot with the performance package in the front. You can clearing see a dual sliding caliper in front in this picture: