I've owned a '99 S2000 for several years now and have slowly turned it into a track car.
I've spent years salivating over the twins before they were born, done 5+ test drives and put a track prepped BRZ through its paces on a day of lapping the Nurburgring Nordschleife.
I
HATE the S2000 as a weekend toy car. It's a very well built car but has a focus for 9/10ths and up driving. In factory spec and driving it at sane legal speeds is akin to driving a 6th gen civic SI; a sporty civic with b16 'Honda soul'. For taller guys, it's a terrible place to be (personal gripe). Again, the quality of the car is outstanding - Honda took their time in building the vehicle and it shows, it gushes of excellent fit and finish, even after 15 years. But the driving experience, on public roads, is piss-poor: good steering weight but minimal feedback, peaky engine (obviously), high-speed is a buzz kill for cheap thrills, high handling limit is a buzz kill for cheap thrills, a shifter that is fickle outside wot, and it's simply uncomfortable to drive to and from the twisty stuff. Fan boys will find excuses for it, I know I have, but it is what it is - rough.
Now put it on a race track and its one of the most convincing street racecars I've been in. A hardtop, half cage and Rival S tires and it'll be a poor(er) mans Cayman GT4. I started modding the car to be autocrossing friendlier about 2 years ago - AEM EMS, test pipe, throttle body/intake manifold, 245 square tires on 17x9 wheels, brakes/fluids/baffles/bars/catch can/rad/cooling/etc. The engine feels like an early 90s VW VR6 engine with schrick cams - great midrange punch to redline pull - power throughout the range in reasonable gear. Now it's going full race car mode with a cage, seats, harness and either chopped windshield ala le mans style or hardtop ala gt3 style. Bigass wing to come either way
At any event I've got a dog pant smile on inside my helmet when driving the S2000, it feels like it's doing what it was meant to do.
I can't speak so much about the twins as a weekend car... Every test drive in recent memory had me fall in love with the car. It's a foil to the S2000, it's fun factor is entirely accessible at legal and sane speeds. I love the (relative) comfort level inside the cabin, the steering feedback, the less-is-more power and linear delivery. It's a different philosophy, another recipe of a lamb dish, so to speak. I giggle when I drive the twins, even more so than any in any of the miata's I've owned. It's simply a balanced car for public roads - Cyndi Lauper girls-wanna-have-fun fun, as much fun as a $600 1985 MR2 you're borrowing from a friend. That being said... I'm getting older and I don't drive on mountain or canyon roads above the speed limit anymore. That thrill is gone and replaced with guilt/anxiety (family to feed). I don't blame others for chasing that green fairy, though, and the twins are just the drink for it.
But on track that's where the BRZ fell short in my experience with Rent4Ring's track-prepped car. I much more enjoyed the Stage 2 Swift I've spent some 25+ NoS laps in than the BRZ. With the Swift you're goated into going beyond limits because the R888 rubber would bail you out (different euro compound apparently) and on track that's awesome - it's a cheap, modest powered fwd hatch that weighs little and you can flick in and out of trouble. The BRZ is an intern applying for a senior consultant position. The linear power band that's great on the street goes flat at the track - more, more, more! Same goes for the chassis and rubber, the cheaper feeling shifting and overall general 'cost' of the car begins to fail to fulfill. Even with a cage and KW suspension & BBK. Not to say it can't feel good but a track BRZ needs more compensation than a track S2K does. That fun balance at 9/10ths+ turns into a glass ceiling. That said, the twins I autocross against put up comparable numbers with fewer mods! E.g. the twins punch above their weight for sure. I will say they don't feel as good doing it, howeer. And there's a philosophical point of identification - do you want a better feeling or better lap times. Me, I don't care about lap times because I benchmark myself, I care only about how big my smile is.
The S2K puts an end-of-days shifter kart smile on my face at the track. It hurts at the end of the day and I feel accomplished. The twins puts a stupid, wonderful, grin on my face at every right turning-lane green light. Switch the rolls and I'm let down by expectations.
And the miata, good lord... I've only had NB's (one stock one modded) and some autocross time in an NC. The miata is like a glock - it's the best. People will convince you their Springfield Armory's, Beretta, CZ (S2000), H&K or Sig (Twins), Walther, etc. are better..and it's arguably personal preference but there's no mistaking the awe inspiring unmatched capability of a Glock - freshly collected or in competitive format, you will undeniably become humbled and a better driver because of time in a Miata. It's an earned smile.