It's neither intrinsically better, worse or a wash. It's different. A crucial trait of the current-generation large-displacement supercharged motors is a sensory experience turbocharging or even massive amounts of displacement alone doesn't deliver.
No matter how many tenths quicker or miles per hour faster or slower one engine may or may not be relative to another, the big, hairy, snarling growl and power delivery of a supercharged V8 with massive amounts of displacement is utterly unique. Combined with the knack Ford developed for imbuing S197 with so much of its retro heritage without being dated, it's a unique combination an IRS will take as much away from as turbocharging or more contemporary styling.
As much of a market as may exist for a futuristically-styled twin-turbo corer carver, especially in markets with entirely different operating economics that lack the same cultural appreciation for much of what resonates so well in North America, S550 will likely be an entirely different experience. Whether it's better or worse will be highly individualized. But, above all, the highest performance versions aren't likely to resemble anything we've known so far.
And even in other markets where turbocharging fewer cylinders has become the standard path to maximum performance, line up a 458, Aventador, Vantage V12 and a Trinity GT500 next to each other, and every smartphone immediately gets pointed at the GT500 first. No matter how much more advanced, sophisticated and refined today's Eurocustomer believes himself to be, ESPECIALLY compared to crude and crass Americans, even they can't ignore the visceral brute force satisfaction lots of big cylinders and belt-driven forced induction alone deliver.
Either way, it's not ONLY about having the biggest or fastest whatever. For those with a tremendous affinity for the Trinity, and even its 5.4 predecessor, it's about something very, VERY specific that transcends "better" or "worse".