You mean the Ecoboost? It looks like on the v6 Decklid there is a Tri-Bar Pony emblem, and on the ecoboost there is just a running pony. That's about the only thing different that I can tell, unless you pop the hood lol.
What about the GT?
That is a good eye on the difference between the Eco and the V6.
They really made the V6, Eco, and GT look almost identical this time around...
Past Mustangs in order and color of text.
(1.)2000, (2.)2004, (3.)2006GT/Auto traded for (4.)2006GT/Manual, (5.)1996, (6.)2011GT, (7.)2003GT, (8.)2006GT, (9.)
2013 Boss 302, and (10.) 2002GT (I have owned a few non Mustang cars over the years as well, but always try to have a Mustang with it or come quickly back to a Mustang!)