Buy the EB
I have an EB Premium...love it. I've driven the GT extensively and just don't like it. More muscle car than sports car. I find the EB much more refined, nimble and balanced. With the sport mode, it's plenty fast.
ecoboost premium
If you go with the eb make sure you get the premium option...it gives you the sport mode option which makes a lot of difference...I have driven thev8 and the eb sport mode and the difference isn't all that much...plus I get 25th in city driving