Disregard this man and all his opinions...
But seriously, all the hate against the Pumas is unwarranted. There were only a few out of hundreds that went bad. They're like 96.2% success rate folks, considering all the ones that were sold. Nothing wrong with Puma turbos. Sheesh. A few reddit posts can do a lot of damage.
I've had my X47 for over 3 years and about 20,000 miles now and it's been flawless.
If I were buying again I'd do a massive amount of research on the S280, Whoosh and other Puma offerings and make up my mind.
I don't know much about the X57 but my best nugget of advice is that 300whp is the perfect spot for this car. Anything above that and the car gets unbalanced. Traction is already an issue at 300 but with good tires and bracing and a good tune my car puts most of the power down. I've ridden in Fiestas with 330whp and 375whp and 400+whp and they can't even get traction in 3rd gear. So my advice for you is get whatever will get you around 300whp and be happy. Sure on YouTube a Fiesta with whatever horsepower can take a Corvette...but that's on a track, with slicks, with the full moon out and on your birthday. Most of us are just trying to enjoy our car on the street. 300hp is where that will happen best on a Fiesta ST.
If you want more get a different car with AWD.