Must be a small guy, for me the '15 interior is far too cramped.
Well I'm 6'4 290 and I test drove a premium Eco Boost today from a dealer I have bought almost all of my Mustangs from. First the car is VERY REFINED. I was really surprised how smooth it was and how it drove. Second, the 15 has more room than my 11 GT500. I had more leg room for sure, and side to side it was a bit bigger. I had m Shelby at the dealer, and Charlie, (my sales guy who has sold me all of my Fords) agreed sitting in both cars.
I would have to say a trick out Eco boost is not a bad deal....not a bad deal at all.