I don't know much about the Borla S-type except what I've read and seen on the internet. However, I agree that if you want something more civilized, the GT 500's might be the perfect fit for you.
I have the GT 500 mufflers (and ProCal), and I love them. I think Ford must have put a lot of time into developing those mufflers, because they are just about perfect in my opinion. They sound even better and are also a little louder with the ProCal tune.
Not only do they sound great, but they are only loud when you would want them to be. I can see them being a little soft for the hardcore crowd, but I'm older and my car is my daily driver. I don't want to be that guy who the neighbors hate and the cops love to harass. Been there, done that, and done did it some more! It's a lot more fun when you are still young and misguided enough to assume that everyone is thinking "Wow, that sounds awesome!" rather than "Look at THIS Jackass!" though...
I first bought Flowmaster American Thunder Series mufflers, and that was a disaster. It was partially my fault for forgetting that I'm not "That Guy" anymore, because they were WAY too loud. But, they were also of the worst quality I've ever seen, they sounded like crap, and they droned so bad they should have been named "The Predator Series". The first set I got had one of the tips welded on crooked, and the other one rattled. The inlet pipes were also crooked, which made it next to impossible to get a good seal.
This was not what I remembered from Flowmaster back in the day, so I swapped them for another set. Same problems. I guess these days they just pick up random undocumented workers from a parking lot somewhere and ask them if they know how to use a welder...and pay them in beer at the beginning of each day!
Oh well, should have just bought the GT 500's to start with, live and learn. I'm going to pick up the Boss 302 side exhaust kit next, which I think should work pretty well with the GT 500 mufflers.
2011 GT Coupe Premium / MT82 / 3.31 / Brembo
Red Candy Metallic / Charcoal Black / 400A
Comfort / Security / HID Headlamps
FRPP M-FR1-MGTB Power Upgrade Package