Yeah I agree with the other posters. Boss is for if you don't want to drive it and it will mostly sit in your garage possibly appreciating in value. 2015 if you are going to drive it a lot.
Jesus, this thread was brought back to life after nearly 4 years. Lol.
Wonder what the OP chose...
Anyway, since it’s been brought back up, tough choice. Subjective to everyone’s opinion, the S550 could be painted with dogshit and it would still look phenomenal. The Boss is a special car and as another post noted, probably very analog compared to the S550. That’s not a bad thing. It’s rowdy and was the king of the NA Mustangs until 2018.