Totally different markets. The WRX is a young persons car with with a more pure and harsher driving experience, not to mention the interior looks very cheap compared to the Stinger.
The Stinger is more of a luxury sports sedan, with lots of, soft-touch material (leather), higher than average plastic quality (when it’s present), and spacious inside.
I think Kia is pushing real hard to become a contender to higher end luxury sedans, and I quite honestly think they hit it out the park. I’d compare it to something like Acura, Lexus, and in some ways Cadillac.