I went from a 2000 GT to a 2013 5.0 and can attest to the suspension improvements.
I agree that the S197 feels bigger. Part of that is the hood feels like it covers about a quarter of an acre. It just has that great feel of the classic long-hood short-deck stance, if you like that sort of thing. You have the feel of a much more massive car out in front of you than with the SN-95. And when you look at the positioning of the front wheels relative to the SN-95, you can see it's no illusion.
But it does not feel bigger in a bad way. I threw weld-in subframe connectors on my 2000 to make it less flexible and it handled fairly well. But the S197 is worlds apart. I could not believe how much of a revelation the improvement in the chassis was, even just in driving down the Interstate. Beyond the arguments for an independent rear suspension, it really needs nothing IMO.
I love them both. But the S197 is definitely a tighter, if heavier, platform.
Black 2013 Mustang 5.0 MT82 w/401A package and 3.31s
Black 2000 Mustang GT (owned 2001-2013, sold at 177,000 miles)
Brown 1971 Triumph TR6