I've always posed the question "What would the mustang look like today if they had continued with the SN-95 body style?" I've always liked the looks of the '03-'04 Cobra's. When they went from the '04 to the '05 retro style I knew it was a treat, but how far could Ford milk that design before it wasn't a thing anymore? 10 years I guess lol. The '15 is growing on me as the '10-'14 did. I still prefer the S197 to the S550. I've driven a S550, and I gotta tell ya, the interior candy is worth way more than the exterior lol. Still, I wouldn't want the car payment again.
As many have stated, it's only a matter of money to keep up with the Jones'. I put a D1SC on my virtually stock 3v, pushing a bit more than a stock coyote. So as far as performance feel, I'll keep my S197 over a stock S550 w/car payment any day. Looks, I like the way my car looks. No, it doesn't turn heads like the S550, because it's not "the new mustang". When it was cammed, it turned heads by default lol. In a few years, the S550 won't turn as many heads because it will be just another mass-produced car, it will have its own fan club too.
The only thing that bothers me is the "GT" status. I look on craigslist and see 05-09 GT's starting to go below $10k. Supercharged ones still $14k-$20k (depending on owner pride, lol). I KBB'd mine w/67,000 miles and I'm still happy with its KBB value, but when it hits 100k it will tip. I thought about selling and buying a GT500 (in regards to it holding better value) but the truth of that matter is, I drive my car. Every day, every weekend, few times a month. Either way, I drive my car. If you drive a GT500 into 100k/mi it won't hold value as well as one that is garage kept and driven to church. But where is the fun in owning a badass car and not driving it? Who is going to troll the import guys and Super Tankers (Camaro/Challenger) if I don't bring the Ford 3v w/hair-dryer bolt-on to the streets and give them the whoosh?!
When the S197 is totaled or FUBAR, that's when I will trade up. Until then, trolling the streets is why I don't trade up.