I guess my point is the definition of 'better car'.
Slalom, 100' spaced - pretty much a wash. Around 67 mph.
Max lat - mini advantage to MX-5, which runs on summer-only tires.
Stopping distance - small advantage to MX-5, again on summer-only tires.
On the track, equal stock rules, the Kappa dominates.
On the autocross course, equal stock rules, the Kappa dominates.
Interior seating room: Kappa
Trunk Space: MX-5
Styling - beauty is in the eye of the beerholder. Finished top-down look on Kappa, vs. functionality for MX-5 in lieu of styling.
Acceleration - small advantage to MX-5 for slightly better 0-60 and 1/4 mile times.
Safety - a wash. MX-5 has side airbags, but scores are very similar for NHTSA crash ratings. Wait - I guess I have to give it to MX-5 b/c they offer active handling, the base kappas don't. But, then again, you don't have to worry about snow like you do in an MX-5, the kappa base cars come equipped with all-season tires. AND the SKY has standard OnStar.
Ride - prolly a wash.
Fit/Finish/Polish - small advantage to MX-5.
Quality - we'll have to see in the future. Prolly MX-5 advantage here.
Appeal - new-kid-on-the-block with fresh styling vs. traditional loyalists that will not relinquish the title of 'best small convertible sports car' at the drop of a hat.
It all depends on what you care about. If you're interested in 'integrated results', the Kappa is the better car. It gets around in snow, the MX-5 doesn't, and it dominates at a race course, which is a really good indicator of how well the car is balanced for the three attributes of accelerating, stopping, and turning.
If you are an MX-5 loyalist, nothing will convince you otherwise.
If you're into the 'newest and best looking, attention grabbing car,' my own personal experience - I never get a 2nd look when I drive an MX-5. I can hardly fuel up a kappa without SOMEONE asking me about the car. The kappa is the better car.
If you care about luggage room and quality reputation, then the MX-5 will probably be a better car for you.
and the list goes on...