It's not quite the question being asked, but I went from a FL 2018 S3 Sportback to a PFL 2016 RS3 a few months ago...
The overwhelming impression I get from the RS3 in comparison to the S3 is of weight and authority. It's a much meatier feel to the steering and, despite larger wheels and less suspension travel, the RS rides more comfortably on the whole. The S3 hardly danced down a B road, yet by comparison again the RS feels like it's bludgeoning undulations and imperfections into submission. I guess the damping rates are probably a little slower in the RS3.
I personally wouldn't swap from the "lesser" car on account of handling alone, but the RS3 package as a whole surprised me with how differently it feels - every drive is an experience and I would certainly put in a recommendation for a PFL with sports exhaust if you are otherwise only considering a FL. I personally feel there is a narrowing opportunity to own a big-engined hatchback at reasonably affordable prices, while they're still modern enough to use every day. The likes of the Golf R32, Alfa 147 GTA, M140i etc with 3.0+ engines are already history, so too will be the 2.5 5-cylinder RS3 soon enough...