I just went through this, sold my '12 GT with the Brembo brakes for good $$. I loved that car, but she had a lot of miles and it was time. I needed a new daily driver.
I drove a low mileage 2013 Boss and a 2016 GT with PP. both cost the same ($37k). The Boss was fun to drive, and faster in a straight line. (So say the stats) but the ride quality of the Boss was not as good and the interior was not even close to the '16 in quality. The Boss I looked at had a interior on par with a base GT of the same era (except the steering wheel). The '16 is a much nicer place to spend routine time. Plus the details on the '16 are amazing, from hood blinkers to easy to access hill assist and other gizmos (to turn it off), to switches for steering feel and sport and track modes. If you haven't guessed, I went with the '16. I've only had it a few days, but the more I drive it the more I enjoy the S550.
2016 Triple Yellow GT Premium with Performance Package