There's a real good chance the EB will be the Mustang to buy.
It will be significantly lighter, and that is the most important thing. If it is easy to get to around 400HP without stressing the motor, it will be faster than a 5.0
Time will tell.
From what I have read, the 2015 EB will weigh 3,524 lbs (auto- heaviest). The GT auto will weigh 3,729 lbs or 205 lbs more making 435 hp. On the GT then, that is 8.57 lbs per hp so if the weight of the GT were shaved to that of the EB, it would only need 411 hp to be equal (roughly speaking). So in theory then, get that EB to 411 hp and go toe to toe with a 2015 GT. Only 101 hp needed. Not sure how that could be done for less than the cost of buying a GT.
2011 Mustang GT 5.0, Kona Blue, Auto, Quarter Louvers, Black Bullitt Wheels. GT500 Axleback Exhaust.