Everybody I talk to, they say if you are looking for a 2013 gt500 and can afford it, you do it. Get rid of the terminator and do it. They say no other gt500 is worth it, but the 2013 is for sure. Take that for what it's worth, but if I could do it, I would.
I have an 11 and 04. Love them both but saying the 11-12 isn't a step up is a huge stretch.
The best solution is to have one of each because they do offer such different driving experiences.
If the choice is to only be able to drive one for a day - I would choose the terminator. If it is to choose which when to live with going forward - without question the GT500. And yes 2011/2012 would count in that as well.