Here is one I find myself constantly conflicted upon, and I wont be able to resolve until I've owned both I don't think.
Honda S2000:
vs
FD3S RX-7
For sake of comparison, AP2 vs Spirit R, each the pinnacle of the respective model, arguably.
For me it's very tough. They both, to me, are really great looking inside and out. Probably my two favorite designs to come out of Japan. An athletic, purposeful, minimalism. I can't decide based on looks. Performance is pretty up and the air too, but the RX-7 is probably a little faster and, being turbocharged, responds better to simple modifications. On the other hand, the naturally aspirated F20C or F22C (AP2 USDM) is an absolute gem, one of the most enjoyable engines I've ever experienced. The 13b-rew tends to sound rather sweet & musical whereas the F20c is more snarly. Again, I find it difficult to decide which is better.
vs
Big, well detailed, elegant, individually-lensed analogue gauges in the RX-7:
vs equally well detailed but arguably more effective (going back to purposeful minimalism here) bar-graph tacho and gauges in the S2000:
The 7 is a coupe, the S2k is a roadster. I like both.
If Mazda had made a 20b, normally aspirated third gen RX-7, it would be in my garage right now. As it is, I still love the FD, but the S2000 is also pretty wonderful. Practically speaking, the S2000 wins out due to reliability and cost to run, but when you see an FD in person, they have swoon-inducing beauty that makes all the pain and torment worth it.
Answer: Both.